Synthesis and Characterization of Novel Hydrolytically Degradable Polyesters

Six novel hydrolytically degradable polyesters were synthesized from thiodipropionic acid(TDPA)and five diols by melt polycondensation,and characterized by FT-IR,1H NMR,gel permeation chromatography,differential scanning calorimetry and thermogravimetry analysis.The polystyrene-equivalent number-average(Mn)and weight-average molecular weight(Mw)of these polyesters ranged from 4900-11100 Da and 7900-20879 Da,respectively,with PDI values of 1.48-1.98.The melting point varied from 62.3-127.9℃,and the 50%mass-loss temperature ranged between 387-417℃.The degradation of these polyesters was studied in terms of relative weight loss in distilled water at different pH.Weight losses of 14%-26%were obtained at pH 7.0,26%-38%at pH 6.0,and 32%-43%at pH 8.3 over a 20-week period.The ecotoxicity study suggested that safety of the synthesized polyesters for the eisenia foetida.These results indicate that these polyesters have a combination of good thermal and degradability behaviors,which can be tailored through selection of the diol monomers used in the synthesis.

Synthesis and Characterization of Poly(terephthalic acid-2,5-furandicarboxylic acid-1,8-octanediol) Copolyester

Terephthalic acid,2,5-furandicarboxylic acid and 1,8-octanediol were adopted as monomers and antimony trioxide as catalyst,and poly(terephthalic acid-2,5-furandicarboxylic acid-1,8-octanediol) copolyesters identified as PEOT-x,where x is the mole fraction of furandicarboxylic acid in the samples,were synthesized by direct esterification.The molecular structure of the copolyesters was characterized by FTIR and 1H NMR spectroscopy.Gel permeation chromatography (GPC),differential scanning calorimetry (DSC),and thermogravimetric analysis (TGA) were used to characterize the molecular weight,molar mass dispersity,glass transition temperature,and thermal stability of the copolyesters,respectively.The mechanical properties of the samples were also investigated.The number-average molecular weight (M_(n)) of the samples varies from 9 700-18 800 g/mol,and molar mass dispersity (■=M_(w)/M_(n)) from 2.15-3.34.The initial decomposition temperature of the copolyesters is in the 332-356 ℃ range,with maximum decomposition rates at 390-410 ℃,while the glass transition temperature (Tg) varies from 0-33 ℃.Mechanical test shows that PEOT-10 has the highest tensile strength,while PEOT-90 has the largest tensile modulus and elongation at break.The experimental results show that these copolyesters can be synthesized with relatively high molecular weights,good thermal stability,and fair mechanical properties,which makes them excellent replacements for commercial polyesters,such as PET,and these properties can be tuned through the relative amounts of biomass monomer 2,5-furandicarboxylic acid used in the reactions.

上市公司控股民营企业后财务整合常见问题研究

近几年,全球经济环境更加复杂多变,我国也出现了"结构调整、产能过剩、增速放缓"的经济局面。为了迎接来自市场的挑战与机遇,企业之间通过资源的整合与合理的配置,进行资源互补,来提升资源的有效利用与管理效率,实现双赢的需求。而并购则是促进企业资源整合与配置的重要方式。加之相关的利好政策,企业之间的并购爆发式增长,在此情况下,作为我国市场经济中坚力量的上市公司,成为了并购的重要参与者。文章结合个人从事并购财务整合的经历,对上市公司并购控股民营企业后在财务整合中常见的问题进行了探讨,并提出财务整合的相关建议。