Light-induced RAFT Polymerization Of PNIPAM And Its Applications For Carbon Materials’ Modification

The temperature-sensitive polymer has a featured ability of temperature response,which indicates great potential for their applications as smart materials.One of the most representative examples is the poly(N-isopropylacrylamide)(pNIPAM),which is synthesized through polymerizing the monomer of N-isopropylacrylamide(NIPAM).NIPAM is an important model of non-ionic hydrophilic monomer.The molecular chain of pNIPAM homopolymer has both hydrophilic and hydrophobic groups,which makes the pNIPAM materials,including the linear pNIPAM and crosslinked pNIPAM hydrogels,exhibit temperature sensitive property.In aqueous solution,the polymer chains shrink when the temperature is above a critical value,and swell when the temperature is below it.Such lower critical solution temperature(LCST)of pNIPAM in aqueous solution is about 32 degree,which is below while approaching the temperature of the human body.This indicates great potential of pNIPAM for applications in the field of biomaterials.However,the applications are somewhat limited by its polymerization method.In this paper,pNIPAM was synthisized by a novel facile and green method.A reversible addition fragmentation chain transfer polymerization process(RAFT)was performed for the preparation of pNIPAM,based on an agent named S-azidepropoxy-carbonylethyl S’-methoxycarbonylphenylmethyl trithiocarbonate(AMP)with azide group,under the irradiation of a sunlight-mimic xenon lamp.During this synthesis process,the AMP took the responsibility of both initiator and chain-transfer agent.The anthracene(-ar)group was further decorated to the end of the pNIPAM chain by click chemistry method,so that the as-obtained polymer(pNIPAM-ar)can easily bind to the surface of certain materials,such as graphene oxide(GO)and carbon nanotube(CNTs),through π-π interactions as surficial modifications to endow the ability of temperaturesensitivity.The structure of the as-fabricated pNIPAM-ar-GO composites was characterized with atomic force microscopy,infrared spectroscopy,laser scanning confocal fluorescence microscopy,and contact angle test,etc.The pNIPAM-ar-GO composite shew temperature-and light-responsive transition between hydrophobic and hydrophilic properties,which can be used for the decoration of material surface for dual-stimuli sensitivity.CNTs,whose inner surface has been modified with pNIPAM(-ar),shew a temperature-sensitive ionic transfer efficiency.This work provides a facile and effective method for the synthesis of pNIPAM(-ar),which broadens its applications for surficial modifications for specifically biological materials.