Thermo-responsive polymers like PNIPAM [poly(N-isopropylacrylamide)] are vital for various applications like sensors, tissue engineering and gene therapy as they exhibit lower critical solution temperature (LCST). It is known that use of low molecular weight imidazolium based ionic liquids (ILs) as a comonomer can alter the LCST of PNIPAM. These can be further tuned to light and temperature using plasmonic nanoparticles (NPs) like Au or Ag. These nanoparticles use the localized surface plasmon resonance (LSPR) to intensify light absorption, due to which its physical properties like refractive index, density and volume changes. This should further, enhance the sensitivity of polymers to both temperature and light. Hence, novel plasmonic NPs incorporated in-situ polymerization of NIPAM/polymerizable IL has been carried out. Au and Ag NPs were synthesized as in literature. 1:0.375 eq. ratio NIPAM: ILs (1-hexyl-3-methylimidazolium acrylate HMImAcr, 1-allyl-3-methylimidazolium chloride AMImCl, 1-allyl-3-octylimidazolium bromide AOImBr and 1-allyl-3-octylimidazolium bis(trifluoromethane)sulphonylimide AOImTFSI) were added to Au/Ag nanoparticles solution with 1mol% N,N,N’,N’-tetramethylethylenediamine initiator and 10 mol% bis(acrylamide). 200 µL of this solution was mixed with 5 µL of 5 wt% ammoniumpersulphate catalyst solution. The material was dried in vacuum at 60 oC overnight. The in-situ polymerization was confirmed using 1H-NMR. The incorporation of gold nanoparticles was characterized using TEM (Fig: 1a) which suggested the presence of NPs on the surface to the material. For Au@PNIPAM-co-HMImAcr, the LCST was found to be around 62 oC using differential scanning calorimetry (DSC) (Fig: 1b). Other novel materials synthesized are being diagnosed for exact LCST. In conclusion, novel plasmonic NPs incorporated ionic liquid copolymers were synthesized which shows enhanced phase transition behavior. This is because NPs hinder the rotation of PNIPAM chains leading to greater need of thermal energy for separation. These materials can be further used for customized applications.

Thermo-sensitive chromic materials using thermosensitive polymer and ionic liquids

255th National Meeting (2018)

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