The poly(2,2-dimethyltrimethylene carbonate)(PDTC)with one hydroxyl and one formate terminal functions was synthesized by in situ generated,tetrahydrosalen stabilized yttrium borohydride complex.The influences of monomer/initiator molar ratio,temperature and reaction time on polymerization of DTC were investigated.Under the condition:[DTC]/[I]=500,55℃,toluene:0.5 mL,DTC:0.6 g,PDTC with M_n=15600 and PDI=2.15 was obtained. Through ~1H-NMR and ^(13)C-NMR analyses,the structure of PDTC was characterized and a coordination-insertion mechanism was proposed.In addition,the random copolymerization of DTC and caprolactone(CL)initiated by rare-earth borohydride compound was studied.The microstructure of PDTC-co-PCL includes four diads:DTC-CL,CL-CL,DTC-DTC and CL-DTC, which were determined by the specific signals in ~1H-NMR spectra.Based on the typical signals of the formate(δ= 8.08)and hydroxyl(δ=3.34)end groups of PDTC-co-PCL,a mechanism involving DTC monomer inserts before CL during the initiation process was presumed.Furthermore,the thermal properties of amorphous copolymer were characterized by differential scanning calorimetry(DSC).The results support the random structure of PDTC-co-PCL.
Tetrahydrosalen ligand was employed in the synthesis of gadolinium complex.The ligand was deprotoned by LiBu,and the afforded lithium salt was reacted with anhydrous GdCl_3 to produce the gadolinium complex through salt metathesis.This complex was successfully used to initiate the ring-opening polymerization ofε-caprolactone.The initiation conditions in different temperature,monomer-to-initiator ratio and time were investigated.Under the condition:[ε-caprolactone]:[catalyst]=600, 56℃,toluene:2 ml,poly(ε-caprolactone)(PCL)with Mw=11,2782 and PDI=1.96 was achieved.
Guang Ming Wu Xu Feng Ni Wei Lin Sun Zhi Quan Shen
In this paper,we report the preparation of a new tertrahydrosalen-stabilized yttrium complex which was employed as an initiator-precursor for the polymerization ofε-caprolactone(ε-CL) in the presence of NaBH_4 to give interesting hydroxytelechelic poly(ε-caprolactone)(PCL).The effect of[monomer]/[initiator]([CL]/[I]),temperature and time on the polymerization was investigated.It was found that under the condition:[CL]/[I]= 1200,55℃,toluene:0.5 mL,ε-CL:0.5 mL,PCL with M_w = 32,600 and PDI = 1.47 was obtained.
Jing Huang Jian Fang Yu Guang Ming Wu Wei Lin Sun Zhi Quan Shen
