Hydration And Thermal Response Behaviours Of Acrylate And Acrylamide Based Thermo-responsive Polymers

This research focusses on the comparison of hydration and thermal response of acrylate and acrylamide based thermo-responsive polymers.Acrylate based thermo-responsive polymers are well known for their flexibility which makes them suitable for application in textile.However,their swelling capability and transition behaviour are not as pronounced as acrylamide based thermo-responsive polymers.To study their differences in hydration and thermal response,polyethyleneglycolmethyletheracrylate(POEGMA300),poly(2-(2(methoxyethoxy)ethyl 2-methyacrylate)(PMEO2MA)and poly(methoxy diethylene glycol acrylate)(PMDEGA)are selected as the acrylate based thermo-responsive polymers.While Poly(N-isopropylacrylamide)(PNIPAM)and poly(N-isopropyl meth acrylamide)(PNIPMAM)are chosen as the acrylamide based thermo-responsive polymers.During this research,a comparison between PMDEGA film and PNIPMAM films are first performed.In situ neutron reflectivity(NR)is used for this investigation.PNIPMAM film presented a much more pronounced swelling capability than the PMDEGA film in the same vapour atmosphere.In addition,the thermal response of hydrated PNIPMAM film under a thermal stimulus is much more abrupt than that of the PMDEGA film.After comparing the homopolymer films,the block copolymer PMEO2MA-b-POEGMA300 is synthesized.The transition behaviour of this block copolymer is studied in solution as well as in thin film.For the synthesis of this block copolymer the atom transfer radical polymerization(ATRP)method is used.First OEGMA300-Br is synthesised,followed by a similar procedure in which OEGMA300-Br is used as initiator and MEO2MA was added to synthesis PMEO2MA-b-POEGMA300.The obtained block copolymer is characterized by H-NMR and GPC to confirm its molecular weight and structure.Then the block copolymer is dissolved in water and the transition behaviour in aqueous solution is investigated.This is performed by UV-Vis spectroscopy and also dynamic light scattering.This shows that PMEO2MA-b-POEGMA300 has two LCST points.The block copolymer self-assembles into micellar structure when the temperature increases.After that,thin films are prepared by spin-coating the block copolymer on silicon wafers.Homogenous thin films with a smooth surface are obtained.The swelling and transition behaviour of the thin film by studied by white light interferometry.In a D2O vapour atmosphere at a constant temperature of 23~°C the film thickness first increases,which shows absorption of the D2O.When the temperature is increased,the film thickness decreases linearly.Once the acrylate based thermo-responsive block copolymer was investigated successfully,a combination of acrylate and acrylamide based block copolymer(PNIPMAM-b-POEGMA300 and PNIPMAM-b-POEGMA300)is attempt to synthesis.To the best of our knowledge,they are not synthesised by ATRP before.Because this block copolymer is a combination of acrylate and acrylamide based thermo-responsive polymers,it is not possible to use the same ATRP method as for PMEO2MA-b-POEGMA300.After a long process of trial,finally these block copolymers are successfully synthesized.Their molecular structures are characterized by H-NMR and GPC.Their behaviour in aqueous solution is studied by UV-Vis.This showed a sharp decrease of transmittance between 35°C and 45°C.This is not unexpected because PNIPAM and PNIPMAM are known for their sharp transition.Further investigations will be performed on their swelling and transition behaviours in thin films.