Graft copolymers having hydrophobic backbone and hydrophilic branches XXXIV. Fabrication and control of honeycomb structure prepared from amphiphilic graft copolymers

Well-controlled polymeric honeycomb structures were made from graft copolymer prepared by free radical polymerization of a poly(ethylene glycol) (PEG) macromonomer and styrene with N,N-azobisisobutyronitrile (AIBN) as radical initiator in ethanol/water (4/1, v/v) solvent. Macroporous polymeric films were formed when chloroform solution of the freeze-dried nanospheres was dip-coated under controlled conditions of humidity and while controlling the composition of the graft copolymer and the type of substrate. Highly-ordered and monodispersed pores were formed on polymeric film surfaces from the graft copolymer (St/(PEG macromonomer) ratio = 105/1, mol/mol) under controlled conditions (humidity, 70% (RH); pulling up speed, 500 cm min(-1)). Control of humidity during the dip-coat process was essential for formation of the ordered porous structure. Macroporous structures were formed possibly by condensed water-droplets as templates. The formation of pores on the film was dependent on concentration of the solution. When dip-coated in a 3 (w/v) % solution, the pores did not penetrate the substrate. In contrast, pores penetrated it from a 1 (w/v)% solution. Graft copolymers formed a unique structure under controlled regulatory conditions.