Poly(propylene carbonate). 1. More about poly(propylene carbonate) formed from the copolymerization of propylene oxide and carbon dioxide employing a zinc glutarate catalyst

被引:141
作者
Chisholm, MH [1 ]
Navarro-Llobet, D [1 ]
Zhou, ZP [1 ]
机构
[1] Ohio State Univ, Dept Chem, Columbus, OH 43210 USA
关键词
D O I
10.1021/ma020348+
中图分类号
O63 [高分子化学(高聚物)];
学科分类号
070305 ; 080501 ; 081704 ;
摘要
Propylene oxide, PO, reacts when heated to 60 C over a zinc glutarate catalyst to form poly(propylene oxide), PPO, which is regioregular, HTHTHT, and favors isotactic triads ii. Under 50 bar of CO2, poly(propylene carbonate), PPC, is formed with less than 5% polyether linkages and with an even smaller component of propylene carbonate, PC. These reactions have been studied as a function of time, and the products have been analyzed by GPC, MALDI-TOF/MS, and C-13 {H-1} NMR spectroscopy. Polymerization of PO yields PPO with -OH and -H end groups, and in the copolymerization of PO and CO2 the low molecular weight chains are readily identified as an alternating copolymer represented as (PO)(n)-alt-(CO2)., where m = n - 1, n - 2, n - 3, n - 4, n - 5, with terminal -OH and -H groups. These results, combined with NMR data, implicate Zn-OH groups as the active initiating species, and furthermore from the molecular weight of the polymer produced at short reaction times, we can infer that some Zn-OH sites are highly active in producing long-chain polymers. The C-13 {H-1} NMR spectra of PPC formed from rac-PO, 50:50 S-PO + rac-PO, and S-PO reveal the preferential formation of HT junctions in the ring-opening of PO by the alkyl carbonate with a HH:HT:TT ratio of 1:3:1. Certain assignments at the diad, triad, and tetrad levels are offered.
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页码:6494 / 6504
页数:11
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