Polyisobutylene-b -Poly(N,N -diethylacrylamide) well-defined amphiphilic diblock copolymer: Synthesis and thermo-responsive phase behavior

Abstract

Polyisobutylene-b-poly(N,N-diethylacrylamide) (PIBb-PDEAAm) well-defined amphiphilic diblock copolymers were synthesized by sequential living carbocationic polymerization and reversible addition-fragmentation chain transfer (RAFT) polymerization. The hydrophobic polyisobutylene segment was first built by living carbocationic polymerization of isobutylene at 270 C followed by multistep transformations to give a welldefined (M w /M n 5 1.22) macromolecular chain transfer agent, PIB-CTA. The hydrophilic poly(N,N-diethylacrylamide) block was constructed by PIB-CTA mediated RAFT polymerization of N,N-diethylacrylamide at 60 C to afford the desired well-defined PIB-b-PDEAAm diblock copolymers with narrow molecular weight distributions (M w /M n 1.26). Fluorescence spectroscopy, transmission electron microscope, and dynamic light scattering (DLS) were employed to investigate the self-assembly behavior of PIB-b-PDEAAm amphiphilic diblock copolymers in aqueous media. These diblock copolymers also exhibited thermoresponsive phase behavior, which was confirmed by UV-Vis and DLS measurements.

Block copolymers derived from polyisobutylene oligomers

“…A variety of prior studies have used radical chemistry or other routes to prepare diblock copolymers from polyisobutylene or other polyolefins . These studies have shown that click chemistry followed by other reactions is one route to diblock PIB derivatives.…”

Utilising alternative modifications of α-olefin end groups to synthesise amphiphilic block copolymers

“…Although this method is conceptually simpler it can be synthetically challenging as stringent reaction conditions are required and only monomers polymerisable via LCP are viable, such as styrene 13 and vinyl ethers. 14 Alternatively, the site transformation also utilises end groups present on PIB but is much more versatile as end group can be modied to a range of polymerisation initiators or mediators compatible with many polymerisations techniques; such as living anionic polymerisation, 15 group transfer polymerisation, 16 reversible addition fragmentation chain transfer (RAFT) polymerisation, 17,18 atom transfer radical polymerisation (ATRP) [19][20][21] and using the same initiators it may be possible to utilise single electron transfer living radical polymerisation (SET-LRP). This allows the polymerisation of other monomer classes like (meth)acrylates and (meth)acrylamides.…”