Liu, Na; Zhang, Jince; Wen, Jingyi; You, Xiaolei; Fang, Dawei published the artcile< Immortal polymerization of LA: the influence of steric effects, electronic effects and pKa on chain transfer agents>, Safety of Triphenylmethanol, the main research area is lactide immortal ring opening polymerization chain transfer agent; steric electronic effect.
The “”immortal”” ring-opening polymerization (iROP) of L-LA, catalyzed by ligand-free Ca[N(SiMe3)2]2(THF)2 in combination with different chain transfer agents (alcs., phenols and PhCH2NH2) was systematically investigated for the first time. When alcs. were used as CTAs (pKa: 14.36-12.73), the polymerization proceeded smoothly and efficiently in excess of PhCH2OH and Ph2CHOH feeding, through which the mol. weights of the obtained PLAs could be precisely controlled by the monomer/alcs. and the mol. weight distributions were maintained at a very narrow level, showing a typically immortal characterization. Upon increasing the steric effect of the alc. (Ph3COH), the activity became lower and the mol. weight distribution became broader than those of PhCH2OH and Ph2CHOH, indicating that the steric effect of alcs. has a significant influence on the iROP of LA. Whereas for the phenol-based CTAs (pKa: 10.17-7.15), the electronic effect was obvious for the ROP of L-LA. The study of the active species indicated that the Ca-O group was the initiation group for alc.- and phenol-based systems. There exists two active species (Ca-NHCH2Ph/Ca-N(SiMe3)2) in the Ca[N(SiMe3)2]2(THF)2/PhCH2NH2 system. The polymerization kinetic behaviors showed that the catalytic activity follows the order of PhCH2OH > Ph2CHOH > PhOH > PhCH2NH2. The kapp of Ph2CHOH increased firstly and then decreased with the increase of the CTA, indicating that the CTA promoted the propagation of polymerization firstly and then decreased the propagation of polymerization
Polymer Chemistry published new progress about Chain transfer agents. 76-84-6 belongs to class alcohols-buliding-blocks, and the molecular formula is C19H16O, Safety of Triphenylmethanol.
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