Two iron-arene complex photoinitiators with different substituents in arene ligands were synthesized, their activities in initiating photopolymerization of cyclohexene oxide (CHO) were compared with that of IRGACURE 2...Two iron-arene complex photoinitiators with different substituents in arene ligands were synthesized, their activities in initiating photopolymerization of cyclohexene oxide (CHO) were compared with that of IRGACURE 261, a commercialized photoinitiator from Ciba-Geigy. A higher activity was found when the arene ligand was substituted with a stronger electron donating group. For the system initiated by IRGACURE 261 the concentration of active centers in CHO polymerization was determined and it was found that the concentration is maximum at around 35℃. The post (dark) polymerization was significant, the polymerization yield decreased with the increase of irradiation temperature and increased with the increase of post polymerization temperature. The results are interpreted based on the mechanism proposed by Lohse, et al..展开更多
Monomer design strategy has become a powerful tool to access polymers with desired and diverse functionalities. Here, we designed a novel monomer 2-((benzyloxy)methyl)-1,4-oxathiepan-7-one (BTO) via installing a benzy...Monomer design strategy has become a powerful tool to access polymers with desired and diverse functionalities. Here, we designed a novel monomer 2-((benzyloxy)methyl)-1,4-oxathiepan-7-one (BTO) via installing a benzyl ether side chain to the structure of 1,4-oxathiepan-7-one (OTO). The ring-opening polymerization of BTO with Zn1 as the catalyst demonstrated the characteristics of living polymerization with turnover frequency (TOF) up to 2520 h^(−1). With a [BTO]_(0)/[Zn1]_(0)/[I]_(0) feed ratio of 2000/2/1, polymer with high number-average molecular weight (Mn = 536 kDa) and narrow dispersity (Ð = 1.06) was obtained. The produced polymer with a glass transition temperature of -17℃ behaved as an elastomer at room temperature. Consequently, the monomer BTO was copolymerized with _(L)-LA to modulate the mechanical properties of P(L-LA). When the BTO content is 10%, the copolymer exhibits excellent strength (24 MPa) and elongation at break (270%), affording a crystalline, hard, and tough plastic material that combines the high ductility of P(BTO) and the high modulus of P(_(L)-LA). In addition, the oxidation of P(BTO) to P(BTO)-SO_(2) led to an improvement of T_(g) from -17℃ to 38℃. Debenzylation of P(BTO)-SO_(2) afforded P(BTO)-SO_(2)-OH containing free hydroxyl groups. Ultimately, P(BTO) could be hydrolyzed under a base condition to recover the corresponding hydroxyl acid intermediate, which could be used to prepare the monomer again and complete the closed-loop from monomer to polymer to monomer.展开更多
基金Supported by the National Natural Science Foundation of China
文摘Two iron-arene complex photoinitiators with different substituents in arene ligands were synthesized, their activities in initiating photopolymerization of cyclohexene oxide (CHO) were compared with that of IRGACURE 261, a commercialized photoinitiator from Ciba-Geigy. A higher activity was found when the arene ligand was substituted with a stronger electron donating group. For the system initiated by IRGACURE 261 the concentration of active centers in CHO polymerization was determined and it was found that the concentration is maximum at around 35℃. The post (dark) polymerization was significant, the polymerization yield decreased with the increase of irradiation temperature and increased with the increase of post polymerization temperature. The results are interpreted based on the mechanism proposed by Lohse, et al..
基金the National Natural Science Foundation of China(51903177 and 22071163)the“1000-Youth Talents Pro-gram",and the Fundamental Research Funds for the Central Uni-versities(YJ201924 and YJ202209).
文摘Monomer design strategy has become a powerful tool to access polymers with desired and diverse functionalities. Here, we designed a novel monomer 2-((benzyloxy)methyl)-1,4-oxathiepan-7-one (BTO) via installing a benzyl ether side chain to the structure of 1,4-oxathiepan-7-one (OTO). The ring-opening polymerization of BTO with Zn1 as the catalyst demonstrated the characteristics of living polymerization with turnover frequency (TOF) up to 2520 h^(−1). With a [BTO]_(0)/[Zn1]_(0)/[I]_(0) feed ratio of 2000/2/1, polymer with high number-average molecular weight (Mn = 536 kDa) and narrow dispersity (Ð = 1.06) was obtained. The produced polymer with a glass transition temperature of -17℃ behaved as an elastomer at room temperature. Consequently, the monomer BTO was copolymerized with _(L)-LA to modulate the mechanical properties of P(L-LA). When the BTO content is 10%, the copolymer exhibits excellent strength (24 MPa) and elongation at break (270%), affording a crystalline, hard, and tough plastic material that combines the high ductility of P(BTO) and the high modulus of P(_(L)-LA). In addition, the oxidation of P(BTO) to P(BTO)-SO_(2) led to an improvement of T_(g) from -17℃ to 38℃. Debenzylation of P(BTO)-SO_(2) afforded P(BTO)-SO_(2)-OH containing free hydroxyl groups. Ultimately, P(BTO) could be hydrolyzed under a base condition to recover the corresponding hydroxyl acid intermediate, which could be used to prepare the monomer again and complete the closed-loop from monomer to polymer to monomer.
