Polydimethylsiloxane: Difference between revisions

{{short description|Chemical compound}}

{{Chembox

| Watchedfields = changed

| verifiedrevid = 458947238

| ImageFile = PmdsStructure.png

| OtherNames = {{Unbulleted list|PDMS|dimethicone|dimethylpolysiloxane|E900}}

|Section1={{Chembox Identifiers

| CASNo = 9006-65-9

| ChemSpiderID = None

| UNII_Ref = {{fdacite|correct|FDA}}

| SMILES = C[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)C

| SMILES_Comment = ''n'' = 12

}}

|Section2={{Chembox Properties

| Formula = {{chem2|CH3[Si(CH3)2O]_{''n''}Si(CH3)3}}

| Density = 0.965 g/cm³

| BoilingPt = N/A, [[glass transition|vitrifies]]

| MeltingPt = N/A, [[glass transition|vitrifies]]

}}

|Section6={{Chembox Pharmacology

| ATCCode_prefix = P03

| ATCCode_suffix = AX05

|Section7={{Chembox Hazards

| NFPA-H = 1

| NFPA-F = 1

| NFPA-R = 0

}}

'''Polydimethylsiloxane''' ('''PDMS'''), also known as '''dimethylpolysiloxane''' or '''dimethicone''', is a [[silicone]] [[polymer]] with a wide variety of uses, from [[cosmetics]] to industrial [[lubrication]] and [[passive daytime radiative cooling]].<ref name="Eylul-et-al_(2022)">{{Cite journal |last1=Simsek |first1=Eylul |last2=Mandal |first2=Jyotirmoy |last3=Raman |first3=Aaswath P. |last4=Pilon |first4=Laurent |date=December 2022 |title=Dropwise condensation reduces selectivity of sky-facing radiative cooling surfaces |journal=International Journal of Heat and Mass Transfer |volume=198 |page=123399 |doi=10.1016/j.ijheatmasstransfer.2022.123399 |s2cid=252242911 |doi-access=free }}</ref><ref>{{cite web | title=Linear Polydimethylsiloxanes |edition=second | website=ECETOC | date=2011-12-28 | url=https://www.ecetoc.org/publication/jacc-report-55-linear-polydimethylsiloxanes-second-edition/}}</ref><ref>{{cite journal | last1=Wolf | first1=Marc P. | last2=Salieb-Beugelaar | first2=Georgette B. | last3=Hunziker | first3=Patrick | title=PDMS with designer functionalities—Properties, modifications strategies, and applications | journal=Progress in Polymer Science | publisher=Elsevier BV | volume=83 | year=2018 | issn=0079-6700 | doi=10.1016/j.progpolymsci.2018.06.001 | pages=97–134| s2cid=102916647 }}</ref>

It is particularly known for its unusual [[rheology|rheological]] (or flow) properties. PDMS is [[Transparency and translucency|optically clear]] and, in general, [[Chemically inert|inert]], [[non-toxic]], and [[non-flammable]]. It is one of several types of [[silicone oil]] ([[polymer]]ized [[siloxane]]). Its applications range from [[contact lenses]] and [[medical devices]] to [[elastomer]]s; it is also present in [[shampoos]] (as it makes hair [[Gloss (optics)|shiny]] and [[slippery]]), food ([[antifoaming agent]]), [[caulk]], [[lubricant]]s and [[Thermal resistance|heat-resistant]] [[tiles]].

==Structure==

The [[chemical formula]] of PDMS is {{chem2|CH3[Si(CH3)2O]_{''n''}Si(CH3)3}}, where ''n'' is the number of repeating [[monomer]] {{chem2|[Si(CH3)2O]}} units.<ref name=West>{{cite book | last1=Mark | first1=James E. | last2=Allcock | first2=H. R. | last3=West | first3=Robert | title=Inorganic Polymers | publisher=Prentice Hall | publication-place=Englewood Cliffs (N.J.) | date=1992 | isbn=0-13-465881-7 | page=}}</ref> Industrial synthesis can begin from [[dimethyldichlorosilane]] and water by the following net reaction:

: {{chem2| ''n'' Si(CH3)2Cl2}} + (''n''+1) {{chem2 | H2O -> HO[Si(CH3)2O]_{''n''}H + 2''n'' HCl }}

The polymerization reaction evolves [[hydrochloric acid]]. For medical and domestic applications, a process was developed in which the [[chlorine]] atoms in the [[silane]] precursor were replaced with [[acetate]] groups. In this case, the polymerization produces [[acetic acid]], which is less chemically aggressive than HCl. As a side-effect, the curing process is also much slower in this case. The acetate is used in consumer applications, such as silicone [[caulk]] and [[adhesive]]s.

===Branching and capping===

[[Hydrolysis]] of {{chem2|Si(CH3)2Cl2}} generates a polymer that is terminated with [[silanol]] groups ({{chem2|\sSi(CH3)2OH}}). These reactive centers are typically "capped" by reaction with [[trimethylsilyl chloride]]:

:{{chem2 | 2 Si(CH3)3Cl + [Si(CH3)2O]_{''n''-2}[Si(CH3)2OH]2 -> [Si(CH3)2O]_{''n''-2}[Si(CH3)2OSi(CH3)3]2 + 2 HCl }}

Silane precursors with more acid-forming groups and fewer methyl groups, such as [[methyltrichlorosilane]], can be used to introduce [[Branching (polymer chemistry)|branches]] or [[cross-link]]s in the polymer chain. Under ideal conditions, each molecule of such a compound becomes a branch point. This can be used to produce hard [[silicone resin]]s. In a similar manner, precursors with three methyl groups can be used to limit molecular weight, since each such molecule has only one reactive site and so forms the end of a siloxane chain.

Well-defined PDMS with a low polydispersity index and high homogeneity is produced by controlled anionic ring-opening polymerization of [[hexamethylcyclotrisiloxane]]. Using this methodology it is possible to synthesize linear block copolymers, heteroarm star-shaped block copolymers and many other macromolecular architectures.

The polymer is manufactured in multiple [[viscosity|viscosities]], from a thin pourable liquid (when ''n'' is very low), to a thick rubbery semi-solid (when ''n'' is very high). PDMS [[molecule]]s have quite flexible polymer backbones (or chains) due to their siloxane linkages, which are analogous to the [[ether]] linkages used to impart rubberiness to [[polyurethane]]s. Such flexible chains become loosely entangled when [[molecular weight]] is high, which results in PDMS' unusually high level of [[viscoelasticity]].

PDMS is [[viscoelastic]], meaning that at long flow times (or high temperatures), it acts like a [[Viscosity|viscous liquid]], similar to honey. However, at short flow times (or low temperatures), it acts like an [[elasticity (physics)|elastic]] [[solid]], similar to rubber. Viscoelasticity is a form of nonlinear elasticity that is common amongst noncrystalline polymers.<ref>{{Cite book |title=Mechanical Behavior of Materials |last=Courtney |first=Thomas H. |date=2013 |publisher=McGraw Hill Education (India) |isbn=978-1259027512 |oclc=929663641}}</ref> The loading and unloading of a stress-strain curve for PDMS do not coincide; rather, the amount of stress will vary based on the degree of strain, and the general rule is that increasing strain will result in greater stiffness. When the load itself is removed, the strain is slowly recovered (rather than instantaneously). This time-dependent elastic deformation results from the long-chains of the polymer. But the process that is described above is only relevant when cross-linking is present; when it is not, the polymer PDMS cannot shift back to the original state even when the load is removed, resulting in a permanent deformation. However, permanent deformation is rarely seen in PDMS, since it is almost always cured with a cross-linking agent.

If some PDMS is left on a surface overnight (long flow time), it will flow to cover the surface and mold to any surface imperfections. However, if the same PDMS is poured into a spherical mold and allowed to cure (short flow time), it will bounce like a rubber ball.<ref name="West" /> The mechanical properties of PDMS enable this polymer to conform to a diverse variety of surfaces. Since these properties are affected by a variety of factors, this unique polymer is relatively easy to tune.<ref>{{cite journal | last1=Seghir | first1=R. | last2=Arscott | first2=S. | title=Extended PDMS stiffness range for flexible systems | journal=Sensors and Actuators A: Physical | publisher=Elsevier BV | volume=230 | year=2015 | issn=0924-4247 | doi=10.1016/j.sna.2015.04.011 | pages=33–39| s2cid=108760684 | url=https://hal.archives-ouvertes.fr/hal-02345519/file/PDMS_Seghir_Arscott.pdf }}</ref> This enables PDMS to become a good substrate that can easily be integrated into a variety of microfluidic and microelectromechanical systems.<ref name=":2" /><ref name="pdms_review" /> Specifically, the determination of mechanical properties can be decided before PDMS is cured; the uncured version allows the user to capitalize on myriad opportunities for achieving a desirable elastomer. Generally, the cross-linked cured version of PDMS resembles rubber in a solidified form. It is widely known to be easily stretched, bent, compressed in all directions.<ref>{{Cite book |title=Polydimethylsiloxane Mechanical Properties Measured by Macroscopic Compression and Nanoindentation Techniques |last=Wang |first=Zhixin |date=2011 |oclc=778367553}}</ref> Depending on the application and field, the user is able to tune the properties based on what is demanded.

[[File:FabricwithinPDMS.jpg|thumb|Fabric embedded within PDMS. This technique enables a user to retain a thin layer of PDMS as a substrate while achieving a higher stiffness through the insertion of reinforcement.]]

[[File:PaperYoungTemperature.png|thumb|Linear relationship in Sylgard 184 PDMS between curing temperature and Young's modulus]]

Overall PDMS has a low elastic modulus which enables it to be easily deformed and results in the behavior of a rubber.<ref name=":0">{{Cite journal |last1=Johnston |first1=I. D. |last2=McCluskey |first2=D. K. |last3=Tan |first3=C. K. L. |last4=Tracey |first4=M. C. |date=2014-02-28 |title=Mechanical characterization of bulk Sylgard 184 for microfluidics and microengineering |journal=Journal of Micromechanics and Microengineering |volume=24 |issue=3 |pages=035017 |doi=10.1088/0960-1317/24/3/035017 |issn=0960-1317 |bibcode=2014JMiMi..24c5017J |doi-access=free|hdl=2299/13036 |hdl-access=free }}</ref><ref name=":1">{{Cite journal |last1=Liu |first1=Miao |last2=Sun |first2=Jianren |last3=Sun |first3=Ying |last4=Bock |first4=Christopher |last5=Chen |first5=Quanfang |display-authors=3|date=2009-02-23 |title=Thickness-dependent mechanical properties of polydimethylsiloxane membranes |journal=Journal of Micromechanics and Microengineering |volume=19 |issue=3 |pages=035028 |doi=10.1088/0960-1317/19/3/035028 |issn=0960-1317 |bibcode=2009JMiMi..19c5028L|s2cid=136506126 }}</ref><ref name="pdms_mechanical" /> Viscoelastic properties of PDMS can be more precisely measured using [[dynamic mechanical analysis]]. This method requires determination of the material's flow characteristics over a wide range of temperatures, flow rates, and deformations. Because of PDMS's chemical stability, it is often used as a calibration fluid for this type of experiment.

The [[shear modulus]] of PDMS varies with preparation conditions, and consequently dramatically varies in the range of 100 kPa to 3 MPa. The [[loss tangent]] is very low {{nobr|(tan δ ≪ 0.001)}}.<ref name="pdms_mechanical">{{cite journal |author1=Lotters, J. C. |author2=Olthuis, W. |author3=Veltink, P. H. |author4=Bergveld, P. |doi=10.1088/0960-1317/7/3/017 |title=The mechanical properties of the rubber elastic polymer polydimethylsiloxane for sensor applications |journal=J. Micromech. Microeng. |year=1997 |volume=7 |pages=145–147 |issue=3 |bibcode=1997JMiMi...7..145L |s2cid=250838683 |url=https://research.utwente.nl/en/publications/the-mechanical-properties-of-the-rubber-elastic-polymer-polydimethylsiloxane-for-sensor-applications(88ad8879-6612-43ae-8a3f-6312b4e2b52b).html }}</ref>

PDMS is [[hydrophobic]].<ref name="pdms_review">{{Cite journal | doi = 10.1002/(SICI)1522-2683(20000101)21:1<27::AID-ELPS27>3.0.CO;2-C| pmid = 10634468| title = Fabrication of microfluidic systems in poly(dimethylsiloxane)| journal = Electrophoresis| volume = 21| issue = 1| pages = 27–40| year = 2000| last1 = McDonald | first1 = J. C. | last2 = Duffy | first2 = D. C. | last3 = Anderson | first3 = J. R. | last4 = Chiu | first4 = D. T. | last5 = Wu | first5 = H. | last6 = Schueller | first6 = O. J. A. | last7 = Whitesides | first7 = G. M. |display-authors=3 | s2cid = 8045677}}</ref> [[Plasma (physics)|Plasma]] [[oxidation]] can be used to alter the surface chemistry, adding [[silanol]] (SiOH) groups to the surface. Atmospheric air plasma and argon plasma will work for this application. This treatment renders the PDMS surface [[hydrophilic]], allowing water to wet it. The oxidized surface can be further functionalized by reaction with trichlorosilanes. After a certain amount of time, recovery of the surface's hydrophobicity is inevitable, regardless of whether the surrounding medium is vacuum, air, or water; the oxidized surface is stable in air for about 30 minutes.<ref name="hydrophobic_recovery">{{cite journal |author1=H. Hillborg |author2=J. F. Ankner |author3=U. W. Gedde |author4=G. D. Smith |author5=H. K. Yasuda |author6=K. Wikstrom |display-authors=3|doi=10.1016/S0032-3861(00)00039-2 |title= Crosslinked polydimethylsiloxane exposed to oxygen plasma studied by neutron reflectometry and other surface specific techniques |journal=Polymer |year=2000 |volume=41 |pages=6851–6863 |issue=18}}</ref> Alternatively, for applications where long-term hydrophilicity is a requirement, techniques such as hydrophilic polymer grafting, surface nanostructuring, and dynamic surface modification with embedded surfactants can be of use.<ref>{{Cite journal|last1=O'Brien|first1=Daniel Joseph|last2=Sedlack|first2=Andrew J. H.|last3=Bhatia|first3=Pia|last4=Jensen|first4=Christopher J.|last5=Quintana-Puebla|first5=Alberto|last6=Paranjape|first6=Makarand|display-authors=3|date=2020|title=Systematic Characterization of Hydrophilized Polydimethylsiloxane|journal=Journal of Microelectromechanical Systems|volume=29|issue=5|pages=1216–1224|doi=10.1109/JMEMS.2020.3010087|issn=1057-7157|arxiv=2007.09138|s2cid=220633559}}</ref>

Solid PDMS samples (whether surface-oxidized or not) will not allow aqueous solvents to infiltrate and swell the material. Thus PDMS structures can be used in combination with water and alcohol solvents without material deformation. However most [[Organic compound|organic]] solvents will [[Diffusion|diffuse]] into the material and cause it to swell.<ref name="pdms_review" /> Despite this, some organic solvents lead to sufficiently small swelling that they can be used with PDMS, for instance within the channels of PDMS [[microfluidic device]]s. The swelling ratio is roughly inversely related to the [[solubility|solubility parameter]] of the solvent. [[Diisopropylamine]] swells PDMS to the greatest extent; solvents such as [[chloroform]], [[ether]], and [[THF]] swell the material to a large extent. Solvents such as [[acetone]], [[1-propanol]], and [[pyridine]] swell the material to a small extent. Alcohols and polar solvents such as [[methanol]], [[glycerol]] and water do not swell the material appreciably.<ref name="solvent_review">{{cite journal |author1=Lee, J. N. |author2=Park, C. |author3=Whitesides, G. M. |doi=10.1021/ac0346712 |title=Solvent Compatibility of Poly(dimethylsiloxane)-Based Microfluidic Devices |journal=Anal. Chem. |year=2003 |volume=75 |pages=6544–6554 |pmid=14640726 |issue=23}}</ref>

===Surfactants and antifoaming agents===

PDMS derivatives are common [[surfactant]]s and are a component of [[defoamer]]s.<ref>{{citation | last1=Höfer | first1=Rainer | last2=Jost | first2=Franz | last3=Schwuger | first3=Milan J. | last4=Scharf | first4=Rolf | last5=Geke | first5=Jürgen | last6=Kresse | first6=Josef | last7=Lingmann | first7=Herbert | last8=Veitenhansl | first8=Rudolf | last9=Erwied | first9=Werner |display-authors=3| title=Ullmann's Encyclopedia of Industrial Chemistry | chapter=Foams and Foam Control | publisher=Wiley-VCH Verlag GmbH & Co. KGaA | publication-place=Weinheim, Germany | date=15 June 2000 | doi=10.1002/14356007.a11_465| isbn=3527306730 }}</ref> PDMS, in a modified form, is used as an [[herbicide]] [[Penetrant (biochemical)|penetrant]]<ref>{{cite web|url=http://www.nrrbs.com.au/chemicalspulse.htm |title=Pulse Penetrant |access-date=3 March 2009 |url-status=dead |archive-url=https://web.archive.org/web/20120220150630/http://www.nrrbs.com.au/chemicalspulse.htm |archive-date=February 20, 2012 }}</ref> and is a critical ingredient in water-repelling coatings, such as {{nowrap|[[Rain-X]]}}.<ref>{{cite web | title=Rain X The Invisible Windshield Wiper | website=Consumer Product Information Database| date=2010-01-29 | url=https://www.whatsinproducts.com/types/type_detail/1/5784 }}</ref>

===Hydraulic fluids and related applications===

Dimethicone is used in the active silicone fluid in automotive viscous limited slip differentials and couplings.

=== Daytime radiative cooling ===

PDMS is a common surface material used in [[passive daytime radiative cooling]] as a broadband emitter that is high in [[Solar reflectance|solar reflectivity]] and [[Emissivity|heat emissivity]]. Many tested surfaces use PDMS because of its potential [[scalability]] as a low-cost polymer.<ref name=":40">{{Cite journal |last1=Simsek |first1=Eylul |last2=Mandal |first2=Jyotirmoy |last3=Raman |first3=Aaswath P. |last4=Pilon |first4=Laurent |date=December 2022 |title=Dropwise condensation reduces selectivity of sky-facing radiative cooling surfaces |journal=International Journal of Heat and Mass Transfer |volume=198 |page=123399 |doi=10.1016/j.ijheatmasstransfer.2022.123399 |s2cid=252242911 |doi-access=free }}</ref><ref name=":26">{{Cite journal |last1=Weng |first1=Yangziwan |last2=Zhang |first2=Weifeng |last3=Jiang |first3=Yi |last4=Zhao |first4=Weiyun |last5=Deng |first5=Yuan |display-authors=3|date=September 2021 |title=Effective daytime radiative cooling via a template method based PDMS sponge emitter with synergistic thermo-optical activity |url=https://www.sciencedirect.com/science/article/pii/S0927024821002488 |journal=Solar Energy Materials and Solar Cells |volume=230 |page=111205 |doi=10.1016/j.solmat.2021.111205 |via=Elsevier Science Direct}}</ref><ref name=":30">{{Cite journal |last1=Fan |first1=Ting-Ting |last2=Xue |first2=Chao-Hua |last3=Guo |first3=Xiao-Jing |last4=Wang |first4=Hui-Di |last5=Huang |first5=Meng-Chen |last6=Zhang |first6=Dong-Mei |last7=Deng |first7=Fu-Quan |display-authors=3|date=May 2022 |title=Eco-friendly preparation of durable superhydrophobic porous film for daytime radiative cooling |url=https://link.springer.com/article/10.1007/s10853-022-07292-8 |journal=Journal of Materials Science |volume=57 |issue=22 |pages=10425–10443 |doi=10.1007/s10853-022-07292-8 |bibcode=2022JMatS..5710425F |s2cid=249020815 |via=Springer}}</ref> As a daytime radiative cooling surface, PDMS has also been tested to improve [[solar cell efficiency]].<ref name=":39">{{Cite journal |last1=Wang |first1=Ke |last2=Luo |first2=Guoling |last3=Guo |first3=Xiaowei |last4=Li |first4=Shaorong |last5=Liu |first5=Zhijun |last6=Yang |first6=Cheng |display-authors=3|date=September 2021 |title=Radiative cooling of commercial silicon solar cells using a pyramid-textured PDMS film |url=https://www.sciencedirect.com/science/article/abs/pii/S0038092X21006010 |journal=Solar Energy |volume=225 |page=245 |doi=10.1016/j.solener.2021.07.025 |bibcode=2021SoEn..225..245W |via=Elsevier Science Direct}}</ref>

===Soft lithography===

{{Further|Photopolymer}}

PDMS is commonly used as a stamp resin in the procedure of [[soft lithography]], making it one of the most common materials used for flow delivery in [[microfluidics]] chips.<ref>{{cite web | title=Introduction to poly-di-methyl-siloxane (PDMS) |publisher=Elvesys | date=2021-02-05 | url=https://www.elveflow.com/microfluidic-reviews/general-microfluidics/the-poly-di-methyl-siloxane-pdms-and-microfluidics/ | last1=Casquillas | first1=Guilhem Velvé |last2= Houssin |first2=Timothée }}</ref> The process of soft lithography consists of creating an elastic stamp, which enables the transfer of patterns of only a few nanometers in size onto glass, silicon or polymer surfaces. With this type of technique, it is possible to produce devices that can be used in the areas of optic telecommunications or biomedical research. The stamp is produced from the normal techniques of [[photolithography]] or [[electron-beam lithography]]. The resolution depends on the mask used and can reach 6&nbsp;nm.<ref>{{cite book |last = Waldner |first = Jean-Baptiste | author-link = Jean-Baptiste Waldner |title = Nanocomputers and Swarm Intelligence |publisher = John Wiley & Sons|place = London |year = 2008|pages = 92–93 |isbn = 978-1-84704-002-2}}</ref>

The popularity of PDMS in microfluidics area is due to its excellent mechanical properties. Moreover, compared to other materials, it possesses superior optical properties, allowing for minimal background and autofluorescence during fluorescent imaging.<ref>{{Cite journal|last1=Piruska|first1=Aigars|last2=Nikcevic|first2=Irena|last3=Lee|first3=Se Hwan|last4=Ahn|first4=Chong|last5=Heineman|first5=William R.|last6=Limbach|first6=Patrick A.|last7=Seliskar|first7=Carl J.|display-authors=3|date=2005|title=The autofluorescence of plastic materials and chips measured under laser irradiation|url=http://dx.doi.org/10.1039/b508288a|journal=Lab on a Chip|volume=5|issue=12|pages=1348–1354|doi=10.1039/b508288a|pmid=16286964 |issn=1473-0197}}</ref>

In [[Bio-MEMS|biomedical (or biological) microelectromechanical systems]] (bio-MEMS), soft lithography is used extensively for microfluidics in both organic and inorganic contexts. Silicon wafers are used to design channels, and PDMS is then poured over these wafers and left to harden. When removed, even the smallest of details is left imprinted in the PDMS. With this particular PDMS block, hydrophilic surface modification is conducted using [[Plasma etcher|plasma etching]] techniques. Plasma treatment disrupts surface silicon-oxygen bonds, and a plasma-treated glass slide is usually placed on the activated side of the PDMS (the plasma-treated, now hydrophilic side with imprints). Once activation wears off and bonds begin to reform, silicon-oxygen bonds are formed between the surface atoms of the glass and the surface atoms of the PDMS, and the slide becomes permanently sealed to the PDMS, thus creating a waterproof channel. With these devices, researchers can utilize various surface chemistry techniques for different functions creating unique lab-on-a-chip devices for rapid parallel testing.<ref name=":2">{{Cite journal | doi = 10.1016/S1369-7021(05)00702-9 | last1 = Rogers | first1 = J. A. | last2 = Nuzzo | first2 = R. G. | year = 2005 | title = Recent progress in Soft Lithography. In | journal = Materials Today | volume = 8 | issue = 2| pages = 50–56 | doi-access = free }}</ref>

PDMS can be [[cross-link]]ed into networks and is a commonly used system for studying the elasticity of polymer networks.{{Citation needed|date=March 2009}} PDMS can be directly patterned by surface-charge lithography.<ref>{{cite journal|title=Surface-charge lithography for direct pdms micro-patterning|author1=S. Grilli |author2=V. Vespini |author3=P. Ferraro |journal= Langmuir |volume=24|pages=13262–13265|year=2008|doi=10.1021/la803046j|pmid=18986187|issue=23}}</ref>

PDMS is being used in the making of synthetic [[gecko adhesion]] dry adhesive materials, to date only in laboratory test quantities.<ref>{{cite press release |url=http://www.umass.edu/newsoffice/newsreleases/articles/146885.php |title=Inspired by Gecko Feet, UMass Amherst Scientists Invent Super-Adhesive Material |archive-url=https://web.archive.org/web/20120223092733/http://www.umass.edu/newsoffice/newsreleases/articles/146885.php |archive-date=2012-02-23 |date=16 Feb 2012 |publisher=UMass}}</ref>

Some [[flexible electronics]] researchers use PDMS because of its low cost, easy fabrication, flexibility, and optical transparency.<ref>{{Cite journal | doi = 10.1038/srep01098| title = Flexible packaging of solid-state integrated circuit chips with elastomeric microfluidics| journal = Scientific Reports| volume = 3| pages = 1098| year = 2013| last1 = Zhang | first1 = B. | last2 = Dong | first2 = Q. | last3 = Korman | first3 = C. E. | last4 = Li | first4 = Z. | last5 = Zaghloul | first5 = M. E. |author5-link = Mona Zaghloul |display-authors=3| bibcode = 2013NatSR...3E1098Z| pmc = 3551231 }}

</ref> Yet, for fluorescence imaging at different wavelengths, PDMS shows least autofluorescence and is comparable to BoroFloat glass.<ref>{{Cite journal|last1=Piruska|first1=Aigars|last2=Nikcevic|first2=Irena|last3=Lee|first3=Se Hwan|last4=Ahn|first4=Chong|last5=Heineman|first5=William R.|last6=Limbach|first6=Patrick A.|last7=Seliskar|first7=Carl J.|display-authors=3|date=2005-11-11|title=The autofluorescence of plastic materials and chips measured under laser irradiation|url=https://pubs.rsc.org/en/content/articlelanding/2005/lc/b508288a|journal=Lab on a Chip|language=en|volume=5|issue=12|pages=1348–1354|doi=10.1039/B508288A|pmid=16286964 |issn=1473-0189}}</ref>

===Stereo lithography===

{{Main|Stereolithography}}

In stereo lithography (SLA) 3D printing, light is projected onto photocuring resin to selectively cure it. Some types of SLA printer are cured from the bottom of the tank of resin and therefore require the growing model to be peeled away from the base in order for each printed layer to be supplied with a fresh film of uncured resin. A PDMS layer at the bottom of the tank assists this process by absorbing oxygen : the presence of oxygen adjacent to the resin prevents it adhering to the PDMS, and the optically clear PDMS permits the projected image to pass through to the resin undistorted.

===Medicine and cosmetics===

Activated dimethicone, a mixture of polydimethylsiloxanes and [[silicon dioxide]] (sometimes called [[simeticone|simethicone]]), is often used in [[over-the-counter drug]]s as an [[defoamer|antifoaming agent]] and [[carminative]].<ref>{{Cite book|url=https://books.google.com/books?id=7FXXQzQ_zf0C&pg=PA369|page=369|title=Techniques in musculoskeletal rehabilitation|author1=Prentice, William E. |author2=Voight, Michael L. |name-list-style=amp |publisher=McGraw-Hill Professional|year=2001|isbn=978-0-07-135498-1}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=Xhe2wLrSz58C&pg=PA447|page=447|title=Helicobacter Pylori: Basic Mechanisms to Clinical Cure 1998|author1=Hunt, Richard H. |author2=Tytgat, G. N. J. |author3=Pharma, Axcan |name-list-style=amp |publisher=Springer|year=1998|isbn=978-0-7923-8739-8}}</ref> PDMS also works as a moisturizer that is lighter and more breathable than typical oils.

Silicone [[breast implants]] are made out of a PDMS elastomer shell, to which fumed [[amorphous silica]] is added, encasing PDMS gel or [[saline solution]].<ref>{{Cite book|title=Evaluation of sustained release of antisense oligonucleotide from poly DL (lactide-co-glycolide) microspheres targeting fibrotic growth factors CTGF and TGF-β1|url=http://etd.fcla.edu/UF/UFE0001194/burney_k.pdf}}</ref> The use of PDMS in the manufacture of contact lenses was patented (later abandoned).<ref>{{cite patent |country=US|number=20050288196 |status=Abandoned|title=Silicone polymer contact lens compositions and methods of use|pubdate=2005-12-29|gdate= |fdate=2005-06-08|pridate=2004-06-08 |inventor=Gerald Horn||assign=Ocularis Pharma Inc.|class= |url=https://patents.google.com/patent/US20050288196}}</ref>

====Skin====

PDMS is used variously in the cosmetic and consumer product industry as well. For example, dimethicone is used widely in skin-moisturizing lotions where it is listed as an active ingredient whose purpose is "skin protection." Some cosmetic formulations use dimethicone and related siloxane polymers in concentrations of use up to 15%. The [[Cosmetic Ingredient Review]]'s (CIR) Expert Panel, has concluded that dimethicone and related polymers are "safe as used in cosmetic formulations."<ref>{{cite journal|doi=10.1177/1091581803022S204|title=Final Report on the Safety Assessment of Stearoxy Dimethicone, Dimethicone, Methicone, Amino Bispropyl Dimethicone, Aminopropyl Dimethicone, Amodimethicone, Amodimethicone Hydroxystearate, Behenoxy Dimethicone, C24-28 Alkyl Methicone, C30-45 Alkyl Methicone, C30-45 Alkyl Dimethicone, Cetearyl Methicone, Cetyl Dimethicone, Dimethoxysilyl Ethylenediaminopropyl Dimethicone, Hexyl Methicone, Hydroxypropyldimethicone, Stearamidopropyl Dimethicone, Stearyl Dimethicone, Stearyl Methicone, and Vinyldimethicone|year=2003|journal=International Journal of Toxicology|volume=22|pages=11–35|pmid=14555417|last1=Nair|first1=B|author2=Cosmetic Ingredients Review Expert Panel|issue=2 Suppl}}</ref>

====Hair====

PDMS compounds such as amodimethicone, are effective conditioners when formulated to consist of small particles and be soluble in water or alcohol/act as surfactants<ref>{{cite book|author1=Schueller, Randy |author2=Romanowski, Perry |title=Conditioning Agents for Hair and Skin|url=https://books.google.com/books?id=f_ETtcJM_0gC|date=1999|publisher=CRC Press|isbn=978-0-8247-1921-0|page= 273|quote=Amodimethicone is recognized for its extremely robust conditioning and for its ability to form clear products when used in high-surfactant shampoos. Amodimethicone is a useful ingredient in conditioners, gels, mousses, and permanents, but its use in shampoos has proved troublesome due to interactions between the cationic and the anionic surfactants, which can result in compatibility problems. However, the amodimethicone emulsion can be made compatible in high-surfactant-level shampoos}}</ref><ref>{{cite book|author1=Goddard, E. Desmond |author2=Gruber, James V. |title=Principles of Polymer Science and Technology in Cosmetics and Personal Care|url=https://books.google.com/books?id=56R-6Wyyo6IC|date=1999|publisher=CRC Press|isbn=978-0-8247-1923-4|page =299|quote=Amodimethicone is typically an emulsion-polymerized polymer; however, utilizing linear processing technology amodimethicone fluids may be prepared as neat fluids, and then emulsified by a mechanical process as desired. The most widely utilized amodimethicone emulsions contain as the surfactant pair either (1) tallowtrimonium chloride (and) nonoxy- nol-10, or (2) cetrimonium chloride (and) trideceth-10 or -12. These "uncapped" amino- functional silicone compounds may be characterized by a linear or branched structure. In either case, amodimethicone polymers will undergo a condensation cure reaction during drying to form a somewhat durable elastomeric film on the hair, providing wet- and dry- combing benefits, lowering triboelectric charging effects, and increasing softness of the dry hair. They are excellent conditioning agents, often found in conditioners, mousses, setting lotions, and less frequently in 2-in-1 shampoos}}</ref> (especially for damaged hair<ref>{{cite book|author=Iwata, Hiroshi |title=Formulas, Ingredients and Production of Cosmetics: Technology of Skin- and Hair-Care Products in Japan|url=https://books.google.com/books?id=5miBgSRcD4cC|date=2012|publisher=Springer Science & Business Media|isbn=978-4-431-54060-1|page =144|quote=Amodimethicone is the most widely used amino-modified silicone. It has an aminopropyl group attached to the methyl group of Dimethicone. Amodimethicone of various degrees of amino modification are available as well as those that have POP, POE, or an alkyl group attached. Amino-modified silicones are cationic and affinitive to hair keratin. They are particularly highly affinitive to damaged hair, which is anionic due to the presence of [[cysteic acid]]}}</ref>), and are even more conditioning to the hair than common dimethicone and/or dimethicone copolyols.<ref>{{cite book|author1=Barel, André O. |author2=Paye, Marc |author3=Maibach, Howard I. |title=Handbook of Cosmetic Science and Technology, Fourth Edition|url=https://books.google.com/books?id=FAYNAwAAQBAJ|date=2014|publisher=CRC Press|isbn=978-1-84214-564-7|page =567|quote=...and amodimethicone, which is an amino-substituted silicone and silicone quats, which contain permanently quaternized ammonium groups. In general, amodimethicones and silicone quats condition better than dimethicones, which condition better than dimethicone copolyols}}</ref>

====Contact lenses====

A proposed use of PDMS is contact lens cleaning. Its physical properties of low elastic modulus and hydrophobicity have been used to clean micro and nano pollutants from contact lens surfaces more effectively than multipurpose solution and finger rubbing; the researchers involved call the technique PoPPR (polymer on polymer pollution removal) and note that it is highly effective at removing nanoplastic that has adhered to lenses.<ref>{{Cite journal|last1=Burgener|first1=Katherine|last2=Bhamla|first2=M. Saad|date=2020-05-19|title=A polymer-based technique to remove pollutants from soft contact lenses|url=http://www.sciencedirect.com/science/article/pii/S1367048420301053|journal=Contact Lens and Anterior Eye|volume=44|issue=3|page=101335|language=en|doi=10.1016/j.clae.2020.05.004|pmid=32444249|issn=1367-0484|arxiv=2005.08732|s2cid=218673928}}</ref>

====As anti-parasitic====

PDMS is effective for treating [[lice]] in humans. This is thought to be due not to suffocation (or poisoning), but to its blocking water excretion, which causes insects to die from physiological stress either through prolonged immobilisation or disruption of internal organs such as the gut.<ref name=Burgess>{{cite journal| title = The mode of action of dimeticone 4% lotion against head lice, ''Pediculus capitis''| author = Burgess, Ian F.| journal = BMC Pharmacology| year = 2009| volume = 9| doi = 10.1186/1471-2210-9-3|doi-access=free| page = 3| pmid = 19232080| pmc = 2652450}}</ref>

Dimethicone is the active ingredient in an anti-[[flea]] preparation sprayed on a cat, found to be equally effective to a widely used more toxic [[pyriproxifen]]/[[permethrin]] spray. The parasite becomes trapped and immobilised in the substance, inhibiting adult flea emergence for over three weeks.<ref>{{cite journal | last1=Jones | first1=Ian M. | last2=Brunton | first2=Elizabeth R. | last3=Burgess | first3=Ian F. | title=0.4% Dimeticone spray, a novel physically acting household treatment for control of cat fleas | journal=Veterinary Parasitology| volume=199 | issue=1–2 | year=2014 | issn=0304-4017 | doi=10.1016/j.vetpar.2013.09.031 | pages=99–106| pmid=24169258 }}</ref>

===Foods===

PDMS is added to many cooking oils (as an anti-foaming agent) to prevent oil splatter during the cooking process. As a result of this, PDMS can be found in trace quantities in many fast food items such as [[McDonald's]] [[Chicken McNuggets]], french fries, hash browns, milkshakes and smoothies<ref>{{cite web| url = http://www1.mcdonalds.ca/NutritionCalculator/IngredientFactsEN.pdf| title = McDonald's Food Facts: Ingredients| date = 2013-09-08| publisher = McDonald's Restaurants of Canada Limited| page = 13

}}</ref> and Wendy's french fries.<ref>{{cite web| url = https://menu.wendys.com/en_US/product/french-fries/| title = Wendy's: Menu: French Fries - Ingredients| access-date = 2022-11-14| publisher = Wendy's International, Inc.}}</ref>

Under European food additive regulations, it is listed as '''[[E Number|E900]]'''.

=== Condom lubricant ===

PDMS is widely used as a [[condom]] lubricant.<ref>{{cite journal | last1 = Coyle | first1 = Tiernan | last2 = Anwar | first2 = Naveed | year = 2009 | title = A novel approach to condom lubricant analysis: In-situ analysis of swabs by FT-Raman Spectroscopy and its effects on DNA analysis | journal = Science & Justice | volume = 49 | issue = 1| pages = 32–40 | doi = 10.1016/j.scijus.2008.04.003 | pmid = 19418926 }}</ref><ref>{{cite journal | last1 = Blackledge | first1 = R. D. | last2 = Vincenti | first2 = M. | year = 1994| title = Identification of polydimethylsiloxane lubricant traces from latex condoms in cases of sexual assault | journal = Journal of the Forensic Science Society | volume = 34 | issue = 4| pages = 245–256 | pmid = 7844517 | doi = 10.1016/s0015-7368(94)72928-5 }}</ref>

=== Domestic and niche uses ===

Many people are indirectly familiar with PDMS because it is an important component in [[Silly Putty]], to which PDMS imparts its characteristic viscoelastic properties.<ref>{{cite web|url=http://www.fluorous.com/journal/?p=86 |title=Micro Total Analysis Systems, Silly Putty, and Fluorous Peptides |website=fluorous.com |date=January 18, 2008 |archive-url=https://web.archive.org/web/20101219102013/http://www.fluorous.com/journal/?p=86 |archive-date=2010-12-19 |url-status=dead}}</ref> Another toy PDMS is used in is [[Kinetic Sand]]. The rubbery, vinegary-smelling silicone caulks, adhesives, and aquarium sealants are also well-known. PDMS is also used as a component in [[silicone grease]] and other silicone based [[lubricant]]s, as well as in [[defoamer|defoaming agents]], [[release agent|mold release agents]], damping fluids, [[heat transfer]] fluids, polishes, [[cosmetics]], hair conditioners and other applications.

It can be used as a [[sorbent]] for the analysis of headspace ([[dissolved gas analysis]]) of food.<ref>{{Cite journal | doi = 10.1021/jf010877x| pmid = 11804511| title = Headspace Sorptive Extraction (HSSE), Stir Bar Sorptive Extraction (SBSE), and Solid Phase Microextraction (SPME) Applied to the Analysis of Roasted Arabica Coffee and Coffee Brew| journal = Journal of Agricultural and Food Chemistry| volume = 50| issue = 3| pages = 449–59| year = 2002| last1 = Bicchi | first1 = C. | last2 = Iori | first2 = C. | last3 = Rubiolo | first3 = P. | last4 = Sandra | first4 = P. }}</ref>

==Safety and environmental considerations==

According to ''[[Ullmann's Encyclopedia of Industrial Chemistry]]'', no "marked harmful effects on organisms in the environment" have been noted for siloxanes. PDMS is nonbiodegradable, but is absorbed in waste water treatment facilities. Its degradation is catalyzed by various [[clay]]s.<ref>{{Ullmann | last=Moretto | first=Hans‐Heinrich | last2=Schulze | first2=Manfred | last3=Wagner | first3=Gebhard | title=Silicones | doi=10.1002/14356007.a24_057}}</ref>

* [[(3-Aminopropyl)triethoxysilane]]

* [[Cyclomethicone]]

* [[Polymethylhydrosiloxane]] (PMHS)

* [[Silicone rubber]]

* [[Silicone]]

* [[Siloxane]] and other [[organosilicon]] compounds

{{reflist|30em}}

==External links==

*[http://www.silicone.jp/e/products/personalcare/pdf/KF/KF-8004.pdf Amodimethicone] Amodimethicone structure and properties

{{Anti-arthropod medications}}

<!---Place all category tags here-->

[[Category:Biomaterials]]

[[Category:Siloxanes]]

[[Category:E-number additives]]