Formation of Nanoscale Networks: Selectively Swelling Amphiphilic Block Copolymers with CO2-Expanded Liquids
writer：Jianliang Gong , Aijuan Zhang , Hua Bai , Qingkun Zhang , Can Du , Lei Li , Yanzhen Hong and J
keywords：CXL,CO2/methanol
source：期刊
specific source：http://pubs.rsc.org/en/content/articlelanding/2012/NR/C2NR33188H#!divAbstract
Issue time：2012年
Polymeric films with nanoscale network were prepared by selectively swelling amphiphilic diblock copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP), with CO2-expanded liquid (CXL), CO2/methanol. The phase behavior of CO2/methanol system was investigated both by theoretical calculation and experiments, revealing that methanol can be expanded by CO2, forming homogeneous CXL under the experimental conditions. When treated with CO2/methanol system, the spin cast compact PS-b-P4VP film was transformed into network with interconnected pores in a pressure range of 12–20 MPa and temperature scope 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 the network structures is achieved in short time scale and shows “thermodynamically restricted” character. The resulting polymer networks were employed as templates, for the preparation of polypyrrole networks, by an electrochemical polymerization process. Porous polypyrrole film was used to fabricate a chemoresistor-type gas sensor which showed high sensitivity towards ammonia.