Synthesis of Block, Statistical, and Gradient Copolymers from Octadecyl (Meth)acrylates Using Atom Transfer Radical Polymerization

Abstract

The synthesis of well-defined homopolymers and random, block, and gradient copolymers from octadecyl acrylate (OA) and octadecyl methacrylate (OMA) using atom transfer radical polymerization (ATRP) is reported. Random copolymers were synthesized by the one-pot copolymerization of either tert-butyl acrylate/octadecyl acrylate (Mn,p(tBA-r-OA) = 13 680; Mw/Mn = 1.13) or tert-butyl methacrylate/octadecyl methacrylate (Mn,p(tBMA-r-OMA) = 24 250; Mw/Mn = 1.14) monomer pairs. Additionally, gradient copolymers were prepared by the simultaneous copolymerization of either tert-butyl acrylate/octadecyl methacrylate (Mn,p(tBA-co-OMA) = 21 790; Mw/Mn = 1.25) or tert-butyl methacrylate/octadecyl acrylate (Mn,p(tBMA-co-OA) = 21 900; Mw/Mn = 1.20) monomer pairs. AB and ABA triblock copolymers containing octadecyl groups were also prepared with controlled molar mass and composition. The sequence of blocking was varied starting from either poly(tert-butyl (meth)acrylate) or poly(octadecyl (meth)acrylate) macroinitiators. The halogen-exchange technique allowed preparation of various well-defined polyacrylate−polymethacrylate block copolymers. Furthermore, uniform phase-separated structures were formed in ultrathin films cast from AB diblock copolymers of ptBMA-b-pOMA (Mn = 52 000; Mw/Mn = 1.12) and ptBA-b-pOMA (Mn = 28 750; Mw/Mn = 1.20) as determined from AFM. ABA triblock copolymers of pOMA-b-ptBA-b-pOMA (Mn = 75 900; Mw/Mn = 1.14) and poly(octadecyl methacrylate)-block-poly(n-butyl acrylate)-block-poly(octadecyl methacrylate) (Mn = 74 400; Mw/Mn = 1.16) were also analyzed using AFM.