Synthesis of water-soluble polyisocyanates with the oligo(ethylene glycol) side-chain as new thermoresponsive polymers

Isocyanates with oligo(ethylene glycol) units have been designed and synthesized as 2,5-dioxaheptyl, 2,5,8-trioxadecyl, 3,6,9-trioxaundecyl, and 2,5,8,11-tetraoxatridecyl isocyanates (MeEO sub(2)IC, MeEO sub(3)IC, EtEO sub(3)IC, and MeEO sub(4)IC, respectively). The bulk polymerization of the isocyanates using n-butoxy( eta super(5)-cycl opentadienyl)dichlorotitanium(iv) at 10 degree C proceeded viaa living manner to produce well-defined water-soluble polyisocyanates of PMeEO sub(3)IC, PEtEO sub(3)IC, and PMeEO sub(4)IC except for PMeEO sub(2)IC. The phase transition property of the obtained polyisocyanates was estimated by their cloud point temperatures (T sub(cp)s) in an aqueous solution (40 g L super(-1)). For PMeEO sub(3)IC, the T sub(cp) decreased from 90.0 to 74.9 degree C with the increasing molecular weight (M sub(n,NMR)) from 1960 to 9000 g mol super(-1). The T sub(cp) of 94.0 degree C for PMeEO sub(4)IC (4460 g mol super(-1)) was higher than that of 79.6 degree C for PMeEO sub(3)IC (4560 g mol super(-1)), and the T sub(cp) decreased from 79.6 to 34.7 degree C by changing from the methyl to the ethyl group in the oligo(ethylene glycol) units from PMeEO sub(3)IC to PEtEO sub(3)IC (4470 g mol super(-1)).