The Study Of Hydrogen Bonding Effects On N-Phenylmaleimide In Controlled Radical Polymerization

Hydrogen bonding is a kind of weak intermolecular force,applied comprehensively in controlled radical polymerization.Molecule weight,polydispersity,tacticity and macromolecule sequence were confirmed that could be controlled by the effect of hydrogen bonding,which might enable the achievement of the synthesis of precise-controlled polymers.Adopting monomers that contain hydrogen bonding receptors and fluoroalcohol solvents that act as hydrogen bonding donor,is the most typical method to construct hydrogen bonding effect in polymerization.Our research group has reported the successful controlled radical polymerization of N-vinyl-2-pyrrolidone(NVP),2-vinyl pyridine(2VP),4-vinyl pyridine(4VP)and methyl methacrylate(MMA),preliminarily illustrated the remarkable performances in the control of polymerization.Classical hydrogen bonding receptor monomer N-phenylmaleimide(N-PMI)was set as the main research target in this article,styrene(St)and 1-octene were chosen as comonomers resectively,investigated the influences which hydrogen bonding exerted in strict alternating copolymerization and the adjustment of macromolecule sequence via reversible addition-fragmentation chain transfer polymerization(RAFT)methodology.Meanwhile,careful analysis and characterizations on optimized geometry,electron cloud,molecular electrostatic potential(MEP)surface and molecular orbital were made by the computer simulation.The detailed studies were established following:(1)The RAFT copolymerization of N-PMI and St was realized with using the azodiisobutyronitrile(AIBN)as initiator,2-cyanoprop-2-yl dithionaphthalenoate(CPDN)as RAFT agent,1,1,1,3,3,3-hexafluoro-2-propanol(HFIP)and toluene as main solvents.The experimental result indicated that the shortening of induction period,the acceleration of copolymerization rate and the deviation of strict alternating copolymerization could be achieved by fluoroalcohols,especially HFIP,when made comparison with non-hydrogen bonding donor solvent,such as toluene.Furthermore,the copolymers obtained from HFIP system showed a conspicuous decline of glass transition temperature(T_g).Elucidations were presented to explicate the phenomena above by the confirmation of computer simulation.(2)The RAFT copolymerization of N-PMI and 1-octene was in progress by one-pot synthetic procedure with using AIBN as initiator,S-(2-cyano-2-propyl)-S-dodecyltrithiocarbonate(CDTC)as RAFT agent,HFIP or chloroform as solvent.The experimental result revealed that hydrogen bonding could promote alternating tendency of N-PMI and 1-octene and the copolymer compositions(unit sequence)from HFIP and chloroform were obviously distinguishable.Then,we designed the time-controlled addition of hydrogen bonding donor solvent in non-hydrogen bonding solvent to adjust the hydrogen bonding interaction in the polymerization system.Since the polymerization proceeded with a controlled manner,two blocks with different copolymer compositions(unit sequence)could be obtained upon the time-controlled addition of different solvent.Characterization of T_g of these copolymers also proved that hydrogen bonding could impact thermal properties of polymer by changing the copolymer compositions with manipulating the hydrogen bonding interaction.