聚对苯二甲酸乙二酯(PET)/聚对乙酰氧基甲酸(PHB)共聚酯及同类共聚物序列分布表征的数学统计

 由聚对苯二甲酸乙二酯(PET)和对-乙酰氧基苯甲酸制得的PET/PHB共聚酯代表了一类序列结构较一般二元共聚物复杂的共聚体系.在揭示了这类共聚物与序列分布有关的诸概率参数中只有一个是独立的之后,定义了参数B_q来描述此类共聚物的无规度.并指出,共聚物B_q=b时的序列分布,可以从一般二元共聚物无规度B=b时的序列结构加以推断.     

用~1H-和~(13)C-NMR方法研究聚对苯二甲酸乙二酯/聚一氧基苯甲酸酯共聚酯的序列分布

测定了PET/30PHB和PET/60PHB共聚酯的高分辨~1H和~(13)C谱,并采用INEPT方法和部分弛豫FT技术确定了季碳吸收峰,对NMR谱进行了归属.应用我们先前提出的方法对共聚酯的序列分布进行了表征.结果表明,两种共聚酯的无规度B_q值均小于1,序列分布不象Jackson等认为的那样为完全无规的.此外,文中还指出,某些研究者套用Flory公式判别PET/PHB共聚酯是否为无规的不妥之处.     

用1H-和13C-NMR方法研究聚对苯二甲酸乙二酯/聚一氧基苯甲酸酯共聚酯的序列分布

 测定了PET/30PHB和PET/60PHB共聚酯的高分辨¹H和¹³C谱,并采用INEPT方法和部分弛豫FT技术确定了季碳吸收峰,对NMR谱进行了归属.应用我们先前提出的方法对共聚酯的序列分布进行了表征.结果表明,两种共聚酯的无规度B_q值均小于1,序列分布不象Jackson等认为的那样为完全无规的.此外,文中还指出,某些研究者套用Flory公式判别PET/PHB共聚酯是否为无规的不妥之处.     

~(13)C-NMR方法研究酚酞聚芳醚酮砜共聚物的序列结构

通过亲核共缩聚合成了一系列酚酞聚芳醚酮砜共聚物和嵌段共聚物 ,并利用1 3C NMR方法研究了共聚物的链结构 ,通过观察酚酞单元中三个位置的季碳原子的化学位移及其相应强度的变化 ,计算共聚物中不同链段的共聚物的组成、平均序列长度和无规度 .结果表明 ,除嵌段共聚物外 ,其它共聚物的无规度均接近 1 ,表明共聚物为无规共聚物 ,而且对三个位置的季碳原子分析均得出了相同的结果 .     

生物可降解共聚物聚丁二酸/对苯二甲酸丁二醇酯(PBST)的序列结构及结晶性研究

制备了高分子量的聚丁二酸丁二醇酯,并通过与对苯二甲酸二甲酯的无规共聚调节其生物可降解性及力学性能,得到了具有优良机械性能和不同生物降解速度的一系列共聚物,并对共聚物序列结构、热力学性能、结晶性进行了研究.结果表明,该共聚物为无规共聚物,PBS和PBT分别结晶.共聚物的结晶熔点符合无规共聚物的Flory方程.     

乙丙共物聚的结晶速率与序列结构

本文用(体)热膨胀计法研究了共聚物组成、催化体系对乙丙共聚物结晶速率的影响。结果表明,同一催化体系乙丙共聚物的最大结晶速率(1/t_((1/2)(max)))随共聚物中乙烯含量的增加而增大。不同催化体系对二元乙丙共聚物的1/t_((1/2)(max))次序为:VOCl_3~->V_(5-9~-)>V_((aca?)3~-)。加入活化剂ETCA的各催化体系的二元乙丙共聚物的1/t_((1/2)(max))为VOCl_3~-ETCA>V_(5-9~-)ETCA>V_((ocac)~-)ETCA。结合结晶度、T_g、以及不同序列分布共聚物组成的测定,可推测VOCl_3~-体系乙丙共聚物具有较长的聚乙烯序列结构,V_(5-9~-)体系次之,V_((acac)_3~-)体系的乙丙共聚物分子链有更多的无规结构。     

以化学键为加和单元研究二元共聚物的玻璃化温度

以玻璃化转变的热力学理论为基础,根据相邻C原子的不同取代情况对主链化学键进行分类,假定化学键的刚性能具有加和性,从而对Gibbs-DiMarzio方程进行了修订,提出了新的Tg-序列结构-共聚物组成关系方程.新方程中包含不同三元组序列的摩尔分率和相关均聚物、周期共聚物的Tg,方程中的所有参数可以通过实验测定或计算得到,没有纯粹的拟合参数,在共聚物的结构与Tg之间建立了直接而唯一的关系,因而此方程可以方便地解释各种共聚物Tg-组成关系曲线.如果二元共聚体系的周期共聚物或交替共聚物尚未合成,还可以通过该方程由无规共聚物的Tg-组成曲线对其Tg进行预测.将该方程应用到MMA-St、E-VAc无规共聚物,得到很好的结果.     

辛酸镁催化L-丙交酯与ε-己内酯共聚及其共聚物结构与性能研究

以无毒性的辛酸镁为催化剂催化L-丙交酯和ε-己内酯本体开环共聚合,制备了一系列不同单体配比的共聚物.首先用1H-NMR跟踪了共聚合单体转化率,显示L-LA聚合速率显著快于ε-CL.用13C-NMR分析共聚物微观结构和计算单体单元平均序列长度(LLLe和LCe),表明聚合过程中酯交换反应导致单元序列结构重新分布.随着反应进行,LLLe急剧下降而LCe逐渐增加后稍有降低,游程数逐渐增大,共聚物无规度提高.反应初期主要是一级酯交换反应,二级酯交换反应导致的CLC序列结构在反应后期才观察到.由Fineman-Ross法计算出L-丙交酯和ε-己内酯的竞聚率分别为rLA=23和rCL=0.22,表明在聚合反应初期L-LA单体优先插入聚合物增长链端,形成LL单元长嵌段结构.共聚物组成显著影响单元序列长度,各序列长度随相应单体加入量增加而增长.二级酯交换系数(TII[CLC])随ε-CL含量增加而增大.对于整个组成范围内,根据竞聚率计算的LLLr值始终要大于聚合产物的LLLe,而LCr计算值小于或接近LCe实验值.因此,共聚物单元序列分布随共聚物投料比和反应时间而改变,趋向于无规分布.以DSC和XRD分析了共聚物热性能和结晶性,表明共聚物结晶性与单元序列长度密切相关.所有共聚物只有一个玻璃化转变温度Tg,符合无规共聚物的Fox方程,说明所得共聚物为无规共聚物,或者说包含有相容性嵌段成分的共聚物.     

FTIR与13C NMR研究丁戊共聚物的微观结构及序列分布

采用傅立叶变换红外光谱(FTIR)分析了丁戊共聚物的微观结构,发现采用磷酸酯钕体系得到的丁戊共聚物组成不同,其聚丁二烯链节的顺式-1,4含量为93.1％～97.7％,聚异戊二烯链节的顺式-1,4含量为97.0％～ 97.5％.采用差示扫描量热仪(DSC)测试了丁戊共聚物的玻璃化转变温度,发现丁戊共聚物具有良好的耐低温性能,其玻璃化转变温度随着异戊二烯含量的增加而提高,稍偏离Fox方程,经修正得到的公式为Tg=1.03TgIWI+TgBWB.采用Kelen-Tudos法计算得到丁二烯和异戊二烯的竞聚率分别为1.21和0.73,二者乘积接近于1,表明丁戊共聚物为无规结构.利用碳核磁谱(13C NMR)对丁戊共聚物进行分析,对其二元序列进行了归属,计算得到丁戊共聚物的二元序列浓度以及聚丁二烯链节和聚异戊二烯链节的数均序列长度;采用Bernoullian模型和Markov模型验证了丁戊共聚物的序列分布,发现其序列分布更符合Markov模型,表明磷酸酯钕体系催化丁戊共聚合时,活性链有末端效应.     

乙烯基单体-N-苯基马来酰亚胺共聚物序列结构研究

用NMR谱研究了甲基丙烯酸甲酯(MMA)-N-苯基马来酰亚胺(PMI)、苯乙烯(St)-PMI共聚物的序列结构.结果表明,MMA-PMI共聚物单元属无规序列分布,St-PMI共聚物单元属交替序列分布.由¹HNMR结果可得MMA-PMI共聚物空间立构部分信息,由¹³CNMR三单元组实验结果算得的序列长度与末端基理论计算结果一致,且MMA-PMI共聚物链属一级Markov链.由St-PMI共聚物序列长度与末端基理论计算结果的偏差提出更为合理的增长基元反应.     

Morphology and degradation behavior of aliphatic/aromatic copolyesters

Random and segmented block copolymers of Poly(tetramethylene succinate) (PTMS) and Poly(tetramethylene terephthalate) (PTMT) were synthesized and characterized regarding sequence distribution and crystalline parameters. Biodegradation behaviors of the copolyesters were examined in activated sludge and enzyme solution in terms of CO₂ evolution. It was found that the initial degradation was strongly dependent on the crystallinity in the random copolymer. However, the chemical compositions become a dominant factor at the later stage of degradation. In the case of block copolymers, the biodegradation rate was most significantly affected by size and degree of perfectness of PTMS crystallites.     

Solid state interchain transesterification reactions in macromolecules

Interchain transesterification reactions (ITR) play an important role in high temperature synthesis of most linear polyesters. For example, polyethylene terephthalate (PET) is prepared commercially by heating and distillation of ethylene glycol from a glycol capped oligomer of PET. In this paper, the potential importance of ITR to effect a much wider range of reactions and process is examined. For example, the ability to control the sequence distribution in linear copolyesters is described. In particular, it is shown that one can induce a random sequence distribution in copolyesters by ITR or, conversely, develop an ordered sequence from a random copolyester again by ITR. In one family of liquid crystalline copolyesters an unusual competition between ordering and a thermal Fries rearrangement is described. A whole new family of crosslinked copolyesters has been developed based on this knowledge of ITR. Solid state processing of cured copolyesters into finished articles by ITR has also been demonstrated. These crosslinked copolyesters can be depolymerized back to the starting oligomers by a reverse ITR, providing for the first time a recyclable thermosetting resin.     

STUDY ON POLYSULFONE-POLYESTER BLOCK COPOLYMERS

Synthesis and characterization of a series of Polysulfone (PSF)-Polyester (PEs) block copolymers were studied.The degree of randomness (B) of these block eopolymers was calculated from the intensities of their proton signals in ~1H NMR spectra and lies in the region of 0相似文献   

A comparative study on transreactions induced phase changes in blends of poly(trimethylene terephthalate) and poly(ethylene naphthalate) upon annealing

By using wide-angle X-ray diffraction (WAXD), thermal analysis, scanning and optical microscopy, and nuclear magnetic resonance (NMR) analyses, this study has demonstrated that blends of two semicrystalline polyesters, poly(trimethylene terephthalate) and poly(ethylene naphthalate) (PTT/PEN), were initially immiscible in as-blended state. The process of blend phase/morphology changes upon extended heating/annealing at elevated temperatures was monitored and probed. With reactions induced at heating/annealing at high temperatures (300°C) for long enough times, the original two phases quickly merged into a single phase. NMR analyses have shown that the products of the transreactions are identified as the random copolyesters (termed as EN-TT). From the NMR results, statistical analyses revealed that the average sequence lengths decreased upon heating, and the degree of chain randomness increased with time of heating at the fixed temperature. Upon extended heating, all PTT and PEN chains could be fully transformed into random copolymers of higher randomness with only a single but amorphous phase. Results are compared to another blend system comprised of PEN and a homologous polyester, PPT, of different structure. Influence of polyester structure on transreactions and phase homogenization process is analyzed.     

Equilibrium Copolymerization. III. Sequence Distribution in Equilibrium Copolymer

The sequence distributions for the copolymers generated in three cases of binary equilibrium copolymerization, including the effect of the ultimate unit, are studied theoretically. From the equilibrium sequence distribution functions, the copolymer sequence structure, the number- and weight-average sequence lengths of monomer units, the run number, the randomness parameter, and the fractions of different diads in the copolymer are derived. According to the relation between the parametric variables introduced in the formulas and the equilibrium copolymerization conditions, all of the structural sequence parameters of the resulting copolymers can be predicted from the comonomer feed composition and the equilibrium constants for initiation and propagation. Finally, the relation between the reaction temperature and the structural sequence parameters is given.     

聚对苯二甲酸二甲酯/聚2,5-呋喃二甲酸二甲酯嵌段聚酯的合成与表征

以生物基单体2,5-呋喃二甲酸、乙二醇为原料合成聚2,5-呋喃二甲酸乙二醇酯(PEF)。采用熔融酯交换法以PEF聚酯部分取代聚对苯二甲酸乙二醇酯(PET),制备了系列PET-b-PEF嵌段共聚酯。通过核磁共振仪(NMR)、差示扫描量热仪(DSC)、热失重仪(TGA)、X射线衍射仪(XRD)等技术手段表征了共聚酯的结构和性能。结果表明,该系列共聚酯的玻璃化转变温度(Tg)在75.8~80.3℃之间,且随着PEF链段质量分数的增加,PET-b-PEF嵌段共聚酯的Tg先降低后升高,结晶度和熔融温度逐渐降低。当PEF链段含量高于15%时,共聚酯没有结晶峰。该系列共聚酯具有良好的热稳定性,起始分解温度在392.2~407.9℃之间,与所制备的PET起始分解温度403.3℃接近。且当共聚酯中PEF链段含量低于15%时,起始分解温度均在407℃左右,优于PET的热稳定性。