Study On The Synthesis And Thermal Properties Of Several Biodegradable Polyester-amides

In this paper, several kinds of polyester-amides have been prepared. First, high molecular weight aliphatic polyester-amides were synthesized through a chain extension of the HOOC-terminated aliphatic prepolyesters with2,2’-(1,4-phenylene)-bis(2-oxazoline) under the catalysis of p-toluenesulfonic acid. The optimal chain-extension were showed as follows:the temperature is at180-200℃; the oxazoline/-COOH molar ratio is1.1; the catalysis amount is between0.05-0.1wt%; the reaction time is from1.5to3h. Higher amount of p-TSA and higher temperature than200℃often caused cross-linking reaction during the chain extension, but few hydroxyl terminated groups would hinder the cross-linking reaction. The catalyzed chain-extension mechanism was proposed. DSC and TGA studies showed that the chain-extended PBA and PBS have lower Tm and crystallinity, slower crystallization rate, and less stable compared with the PrePBA or PrePBS because of regularity disruption by incorporating stiffer diesteramide structures in the major polyester structural units.Second, aliphatic-aromatic polyester-amide was prepared by melt polycondensation of1,4-butanediol, adipatic acid and an aromatic bisamide-diol synthesized from dimethyl terephthalate and aminoalcohol, then a chain extension was performed. By varying the ratio of the bisamide-diol to1,4-butanediol, a series of polyesteramides were obtained with the diesterdiamide content between10and100mol%. Less effectivity of the chain extension was got by using ABC or PBOX as chain-extenders alone. High molecular weight polyester-amide was prepared by using ABC and PBOX as combined chain-extenders at T=200℃, ABC:2-OH=1.1(molar ratio) and PBOX:2-COOH=1(molar ratio) for about2h. NMR studies showed that the prepolyester-amides had random structure caused by the ester-amide interchange during the reaction between adipic acid and HETA. After chain extension, Tg increased but the Tm and△Hm decreased compare to the prepolymers when the amide concentration is low. For the polyesteramides with high amide content, they showed relative high Tg and no Tm. The introduced amide groups and the benzene groups may decrease the crystallization ability. The thermal stability decreased with increasing amide content.Third, aliphatic polyester-amide prepolymers were prepared by melt polycondensation of1,4-butanediol, adipatic acid and the bisamide-diols synthesized from the reaction of aminoalcohol with diethyl adipate or diethyl oxalate. The chain extension was then performed at T=200℃ABC:2-OH=1.1(molar ratio) and PBOX:2-COOH=1(molar ratio) for2.5h. By varying the ratios between the bisamide-diol and1,4-butanediol, a series of polyesteramises were obtained with the diesterdiamide content from10and20mol%. FT-IR and1H-NMR analysis revealed that side reaction took place in preparing prePEA(0,x/y) and no side reaction found in preparing prePEA(4,x/y). The Tm and△Hm decreased with increasing the amide content; and the Tm and△Hm also decreased after the chain extension; there were two Tm and△Hm corresponding to the melting of crystals of ester sequences and amide sequences, respectively.