Summary: The stereoselective polymerization of partial rac‐lactide was attempted by using crystallization during polymerization. Polymerizations were carried out with trifluoromethanesulfonic acid in a mixed solvent of toluene and octane. The molar content of L ‐lactate in the feed was 95%. Polymerization proceeded with the elimination of D ‐lactate by means of crystallization. Poly(L ‐lactic acid) (PLLA) crystals were first precipitated and then plate‐like poly(lactic acid) (PLA) crystals were finally obtained, of which the composition of L ‐lactate was 97.6% and the was 1.68 × 104.
The polymerization time dependence of the microstructure of poly(lactic acid), i.e., the percentage of mm triads (mm%), prepared from partial rac‐lactide in toluene‐70. 相似文献
Summary: A novel cyclic carbonate monomer 5‐methyl‐5‐(succinimide‐N‐oxycarbonyl)‐1,3‐dioxan‐2‐one (MSTC) was prepared. The copolymers of MSTC with caprolactone (CL) were further synthesized by ring‐opening copolymerization. The copolymers with amido‐amine pendent groups were obtained by aminolysis of poly(MSTC‐co‐CL) with ethylenediamine. These copolymers were characterized by IR, 1H NMR, 13C NMR spectroscopies and GPC. The hydrophilicity and degradability of the copolymers with amido‐amine pendent groups were greatly improved in comparison with the PCL homopolymer.
Hydrophilicity of PCL (1), poly(MATC‐co‐CL) (16.5:83.5) (2), and poly(MATC‐co‐CL) (29.5:70.5) (3). 相似文献
Summary: The reaction of hydrazine with ethyl glycolate results in 1,2‐bisglycoylhydrazine, a monomer that was used for the lipase‐catalyzed synthesis of biodegradable poly(ester hydrazide)s. The polymers derived from the hydrazide‐containing monomer and vinyl‐activated adipic, suberic, and sebacic acid, respectively, showed low melting temperatures of 136 to 141 °C and are thermally stable up to 300 °C. The aliphatic poly(ester hydrazide)s (PEHs) are highly crystalline, as proven by polarization microscopy and atomic force microscopy. Further, the PEHs represent the first described biodegradable poly(hydrazide)s. They degrade in the presence of lipase at 37 °C within a few weeks.
Summary: Dendrons and dendrimers with cationic amino groups at their periphery were successfully synthesized up to the third and second generation, respectively. The results obtained by 1H NMR spectroscopy and gel permeation chromatography analysis supported the formation of the targeted dendrons and dendrimers. The dendrons were grown via ester linkages, which endowed them with biodegradability in D2O at 37 °C. The degradation rate depends upon the steric hindrance and reactivity caused by the bulkiness and compact structure of the dendrons. All of the synthesized dendrons were degraded within a month, while 60% of the ester groups in the sterically crowded dendrimers were degraded over the same time period. The cytotoxicity of the dendrons was evaluated by the MTT assay on a 293T cell line which indicated that the obtained dendrons were completely non‐toxic. These non‐toxic, biodegradable cationic dendrons and dendrimers are believed to have potential applications in the biomedical field.
Synthetic procedure of dendrons and dendrimers. 相似文献