Synthesis And Characterization Of Responsive Poly(N-vinylcaprolactam)-block-poly(ionic Liquids)

Ionic liquids and environmental-responsive polymer have become research hotspot in its unique performance and the good application prospect.Temperature/pH/ionic-responsive double-hydrophilic diblock Copolymers PNVCL-b-PEVImBr were synthesized and characterized in this paper.Carboxyl-terminated poly(N-vinylcaprolacta)(PNVCL-COOH)were synthesized via free radical chaintransfer polymerization of N-vinylcaprolactam(NVCL)with azobis isobutyronitrile as the initiator,thioglycolic acid as the chaintransfer agent.And the alkynyl-terminated poly(N-vinylcaprolactam)(PNVCL-C?CH)was synthesized by esterification of PNVCL-COOH with 2-methyl-3-butyn-2-ol as the smallmolecular alcohol.The ionic liquids monomers were synthesized with 1-vinyl imidazole and bromine ethane,then polymerized to give PEVImBr-COOH.And the the azido-terminated poly(l-vinyl-3-ethyl bromide imidazole)(PEVImBr-N3)were synthesized by esterification of PEVImBr-COOH with 2-azidoethanol(Azea)as the smallmolecular alcohol.The block copolymers PNVCL-b-PEVImBr were synthesized by click chemistry of alkynyl-terminated poly(N-vinylcaprolactam)(PNVCL-C-?CH)and azido-terminated poly(ionic liquid)(PEVImBr-N3)with(+)-sodiumL-ascorbate(SA)and copper ? sulfatepentahldrate as the catalyst.FT-IR,1H-NMR and GPC were used to demonstrate the structure and their compositions.The self-assembly behavior of these copolymers in aqueous solution was studied by fluorescence technique.The results showed that the CMC of copolymer solution increased with the increasing of the proportion of hydrophobic parts.The micelles were consisted of a relatively hydrophobic core of PEVImBr and a hydrophilic shell of PNVCL in aqueous solution.TEM images demonstrated the micelles are all spherical.On the other hand,the UV-vis?DLS and TEM showed that these diblock copolymers exhibit a reproducible temperature/pH/ionic-responsive behavior.The lower critical solution temperature(LCST)of polymers increased with the decreasing of the solution concentration or the increasing of the proportion of the PNVCL segment.By the introduction of the PEVImBr segment,the LCST of the polymer is reduced.The average size of micelles increased with the increasing of the proportion of the PNVCL segment or PEVImBr segment.And it also increased with the rising of the ionic concentration.