title: Formation of nanoscale networks: selectively swelling amphiphilic block copolymers with CO2-expanded liquids.
abstract: Polymeric films with nanoscale networks were prepared by selectively swelling an amphiphilic diblock copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP), with the CO(2)-expanded liquid (CXL), CO(2)-methanol. The phase behavior of the CO(2)-methanol system was investigated by both theoretical calculation and experiments, revealing that methanol can be expanded by CO(2), forming homogeneous CXL under the experimental conditions. When treated with the CO(2)-methanol system, the spin cast compact PS-b-P4VP film was transformed into a network with interconnected pores, in a pressure range of 12-20 MPa and a temperature range of 45-60 °C. The formation mechanism of the network, involving plasticization of PS and selective swelling of P4VP, was proposed. Because the diblock copolymer diffusion process is controlled by the activated hopping of individual block copolymer chains with the thermodynamic barrier for moving PVP segments from one to another, the formation of the network structures is achieved in a short time scale and shows "thermodynamically restricted" character. Furthermore, the resulting polymer networks were employed as templates, for the preparation of polypyrrole networks, by an electrochemical polymerization process. The prepared porous polypyrrole film was used to fabricate a chemoresistor-type gas sensor which showed high sensitivity towards ammonia.
authors.affiliation: College of Materials, Xiamen University, Xiamen, 361005, PR China.
authors.forename: Jianliang
authors.initials: J
authors.lastname: Gong
authors.forename: Aijuan
authors.initials: A
authors.lastname: Zhang
authors.forename: Hua
authors.initials: H
authors.lastname: Bai
authors.forename: Qingkun
authors.initials: Q
authors.lastname: Zhang
authors.forename: Can
authors.initials: C
authors.lastname: Du
authors.forename: Lei
authors.initials: L
authors.lastname: Li
authors.forename: Yanzhen
authors.initials: Y
authors.lastname: Hong
authors.forename: Jun
authors.initials: J
authors.lastname: Li
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry*; D003460:Crystallization / Q000379:methods*; D046911:Macromolecular Substances / Q000737:chemistry; D000432:Methanol / Q000737:chemistry*; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D011137:Polystyrenes / Q000737:chemistry*; D016062:Porosity; D011725:Pyridines / Q000737:chemistry*; D012996:Solutions; D013499:Surface Properties
chemical_list: D046911:Macromolecular Substances; D011137:Polystyrenes; D011725:Pyridines; D012996:Solutions; D002245:Carbon Dioxide; C029351:4-vinylpyridine; D000432:Methanol