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Highly Efficient One-Pot Synthesis of COS-Based Block Copolymers by Using Organic Lewis Pairs  
Highly Efficient One-Pot Synthesis of COS-Based Block Copolymers by Using Organic Lewis Pairs
资料类型: PDF文件
关键词: metal-free  Lewis  pairs  poly(monothiocarbonate)  block  copolymer  carbonyl  
sulfide  immortal  polymerization  
资料大小: 1126k
所属学科: 高分子化学
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简介:
A one-pot synthesis of block copolymer with regioregular poly(monothiocarbonate) block is described via metal-free catalysis. Lewis bases such as guanidine, quaternary onium salts, and Lewis acid triethyl borane (TEB) were equivalently combined and used as the catalysts. By using polyethylene glycol (PEG) as the macromolecular chain transfer agent (CTA), narrow polydispersity block copolymers were obtained from the copolymerization of carbonyl sulfide (COS) and propylene oxide (PO). The block copolymers had a poly(monothiocarbonate) block with perfect alternating degree and regioregularity. Unexpectedly, the addition of CTA to COS/PO copolymerization system could dramatically improve the turnover frequency (TOF) of PO (up to 240 h??1), higher than that of the copolymerization without CTA. In addition, the conversion of CTA could be up to 100% in most cases, as revealed by 1H NMR spectra. Of consequence, the number-average molecular weights (Mns) of the resultant block copolymers could be regulated by varying the feed ratio of CTA to PO. Oxygen-sulfur exchange reaction (O/S ER), which can generate randomly distributed thiocarbonate and carbonate units, was effectively suppressed in all of the cases in the presence of CTA, even at 80 C. This work presents a versatile method for synthesizing sulfur-containing block copolymers through a metal-free route, providing an array of new block copolymers.
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