Ethyl cellulose amphiphilic graft copolymers with LCST-UCST transition: Opposite self-assembly behavior, hydrophilic-hydrophobic surface and tunable crystalline morphologies

• EC-based graft copolymers were synthesized by ROP and ATRP.
• The amphiphilic copolymers can achieve LCST-UCST transition.
• The copolymers can self-assemble to micelles.
• The hydrophilic-hydrophobic property of the polymers can be adjusted.

Novel and well-defined graft copolymer with block copolymer side chain, ethyl cellulose-graft-(poly(ε-caprolactone)-block-poly(N,N-dimethylaminoethylmeth acrylate)) (EC-g-(PCL-b-PDMAEMA)) with a lower critical solution temperature (LCST) was successfully synthesized via the combination of ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). EC-g-(PCL-b-PDMAEMA) copolymers with various PCL-b-PDMAEMA block lengths were obtained by adjusting the molar ratios of the N,N-dimethylaminoethyl methacrylate monomer to ε-caprolactone. The EC-g-(PCL-b-PDMAPS) with an upper critical solution temperature (UCST) was obtained via facile quaternization reaction of PDMAEMA with 1,3-propane sultone. EC-g-(PCL-b-PDMAEMA) and EC-g-(PCL-b-PDMAPS) micelle solutions showed opposite thermoresponsiviness and hydrophilic-hydrophobic surface. Moreover, the tunable crystalline morphologies could be obtained from these graft copolymers through changing the polymer structure and PDMAEMA contents.