一种新型聚酰胺嵌段共聚物的合成与表征

首先以丁二酸酐(SA)对聚乳酸(PLA)进行改性,得到了一种端羧基聚乳酸(PLA/SA),并将丁二酸和丁二醇通过溶液缩聚反应合成端羧基聚丁二酸丁二醇酯(PBS),然后以2,2'-(1,3-亚苯基)-二噁唑啉(1,3-PBO)为扩链剂,将PLA/SA与PBS交联,合成一种新型含有芳香烃的聚酰胺嵌段共聚物(PLA-PBO-PBS)。采用FTIR、1H-NMR、GPC、DSC、XRD、TGA等测试手段分别对PLA/SA、PBS和PLA-PBO-PBS进行了表征。结果表明:扩链剂1,3-PBO将PLA/SA和PBS成功交联,得到了目标物PLA-PBO-PBS嵌段共聚物。采用1,3-PBO进行扩链改性,能有效提高目标物的分子量,其中当n(PLA/SA):n(PBS):n(1,3-PBO)=1:1:1.2时,目标物PLA-PBO-PBS的数均分子量(Mn)达到62 506,其分子量分布Mw/Mn=2.4。另外,经1,3-PBO扩链改性后,熔融峰消失,PLA和PBS间的交联得到改善;目标物PLA-PBO-PBS结晶度下降、熔程变窄,而且热稳定性得到了一定程度的提高,其柔韧性、延展性和耐热性均有所提高。     

乳酸基聚酯酰胺聚合物的合成及表征研究

以辛酸亚锡和对甲苯磺酸为催化剂,采用梯度升温法,将乳酸(LA)与马来酸酐(MAH)在160℃、压力0.096MPa下直接熔融缩聚得到聚乳酸-马来酸酐共聚物(P(LA/MAH)),再以2,2'-(1,3-亚苯基)-二噁唑啉(1,3-PBO)为扩链剂,扩链得到可生物降解的聚酯酰胺(PEA)。采用乌氏黏度计、FTIR、1H-NMR、DSC、XRD、TGA等测试手段对该聚合物的结构和性能进行了表征。结果表明:扩链反应最佳条件为压力0.096 MPa,温度160℃,羧基和噁唑啉基团的摩尔比n(–COOH):n(–oxazoline)=1:1.6,反应时间20 min;所得PEA的最大黏均摩尔质量(Mη)可达50 097。另外,由于苯环和酰胺基的引入,产物的刚性增强,而且其玻璃化转变温度(Tg)相对于PLA有所提高;其热分解过程为一步分解且热稳定性提高;产物的结晶度仅为0.87%,呈无定形态,其柔韧性比PLA有所增强。     

可生物降解聚乳酸的扩链研究进展

依据聚乳酸(PLA)分子的端羟基和端羧基结构特点,主要综述了近年来以有机小分子扩链改性PLA的方法、机理与应用,分别介绍了端羟基缩聚扩链剂、端羧基缩聚扩链剂以及其他扩链剂在改性PLA中的应用.其中端羟基缩聚扩链剂主要有多异氰酸酯、双环羧酸酐、二酰氯;端羧基缩聚扩链剂主要有二噁唑啉、双环氧化物、二元胺、二元醇.并且简要介绍了其他低聚物如聚乙二醇(PEG)、聚乙醇酸(PGA)、聚己二酸丁二醇酯(PBA)、聚丁二酸丁二醇酯(PBS)、聚占-己内酯(PCL)与PLA共聚提高其摩尔质量及改性方面的研究进展,最后对PLA的改性研究与应用做了进一步的展望.     

软段分子链结构对PUF性能的影响

通过将聚乙二醇(PEG)、聚己内酯(PCL)、聚乳酸(PLA)和聚四氢呋喃醚(PTMG)等不同特性的聚合物链段引入聚氨酯(PU)基体,制备了具有不同软段结构的聚氨酯泡沫塑料(PUF)。考察了不同软段分子链结构对PUF力学性能、热性能及在土壤中降解性能的影响。结果表明,随着软段中PEG或PLA含量的增加,PUF的拉伸强度下降;不同软段结构PUF的玻璃化转变温度顺序为:PTMG1000相似文献   

星形PLA-HTPB聚氨酯共聚物的合成与表征

采用自制的星形聚乳酸(PLA)和端羟基聚丁二烯(HTPB)为主要原料,甲苯-2,4-二异氰酸酯为扩链剂合成了星形PLA-HTPB聚氨酯共聚物,通过FT-IR、DSC、TG等测试手段对此共聚物的结构与性能进行表征。结果表明,星形PLA-HTPB聚氨酯共聚物两相具有各自的玻璃化转变温度,两相之间存在相分离现象;其热分解过程为2步,乳酸链段的起始热分解温度为229℃,表观活化能为83.11kJ/mol,反应为一级反应;丁二烯链段的起始热分解温度为414℃,表观活化能为192.83kJ/mol,反应为非一级反应。     

熔融扩链反应制备PLA／PBAT多嵌段共聚物

以六亚甲基二异氰酸酯(HDI)为扩链剂,在催化剂辛酸亚锡作用下,通过熔融扩链反应制备了聚乳酸(PLA)/聚(己二酸丁二酯/对苯二甲酸丁二酯)(PBAT)多嵌段共聚物.研究了反应时间、温度、扩链剂用量等工艺条件对PLA/PBAT共聚物结构、相对分子质量的影响.用红外光谱仪、核磁共振仪、偏光显微镜等分析手段对PLA、PBAT和PLA/PBAT共聚物进行了分析表征.结果表明,通过扩链反应,PLA的分子链中引入了新的嵌段,其相时分子质量及柔韧性大幅度提高.     

紫外光固化水性聚氨酯丙烯酸酯的制备与性能研究

以异佛尔酮二异氰酸酯(IPDI)为硬段,聚乙二醇(PEG)为软段,以二羟甲基丙酸(DMPA)为亲水扩链剂引入羧基,用甲基丙烯酸-β-羟乙酯(HEMA)进行封端引入碳碳双键作为光固化官能团,通过多步缩聚反应制备出紫外光固化水性聚氨酯丙烯酸酯(UV-WPUA)。探究了DMPA加入量、固含量、光引发剂种类对乳液和涂膜性能的影响。     

端羧基聚乳酸的扩链、改性及其性能

以丙交酯为原料、辛酸亚锡为催化剂、丁二酸酐为改性剂,采用梯度升温法,在150℃、0.098MPa条件下采用直接熔融缩聚法合成端羧基聚乳酸共聚物P(LA/SA),接着用2,2-(1,3-亚苯基)-二 唑啉(1,3-PBO)对其进行扩链,按n(丙交酯)/n(1,3-PBO)= 1/2.4加入1,3-PBO,反应1h制得聚酰胺酯(PEA),最后将高岭土与PEA在150℃、减压条件下熔融复合改性。采用GPC、FTIR、¹H NMR、DSC、SEM等手段对聚合物的结构进行表征和性能测试,结果表明,与P(LA/SA) 相比,扩链产物PEA相对分子质量大幅度提高,重均相对分子质量高达24万,玻璃化转变温度T_g高于PLA和P(LA/SA),改性后复合材料的热稳定性能提高,结晶度降低。     

扩链型UV固化聚氨酯丙烯酸酯的合成及性能研究

以甲苯二异氰酸酯、聚乙二醇、丙烯酸羟乙酯为反应物,并以乙二醇或1,3-丁二醇为扩链剂,合成了扩链型聚氨酯丙烯酸酯,并以其制备了UV固化涂料。研究了聚乙二醇及扩链剂对UV固化涂膜性能的影响。随聚乙二醇相对分子质量的增加,涂膜的柔韧性从4.9 mm变为2.0 mm,硬度从H降低为6B;扩链温度在25~30℃之间时,扩链反应容易控制。扩链后涂膜的表干时间变长,附着性变好,柔韧性小于1 mm,同时涂膜耐水性、耐酸性、耐碱性、耐磨性、耐溶剂性均有所提高。     

PLA/PBAu嵌段共聚物合成工艺优化及降解性能

以端羟基聚乳酸(PLA)、聚己二酸-丁二醇-尿素(PBAu)为预聚物,六亚甲基二异氰酸酯(HDI)为扩链剂,制备出一种新型PLA/PBAu嵌段共聚物。研究了扩链剂用量、扩链温度以及催化剂用量对PLA/PBAu嵌段共聚物分子量的影响,确定了合成PLA/PBAu嵌段共聚物的最佳工艺条件。采用核磁共振、凝胶渗透色谱、差示扫描量热仪、扫描电镜等对共聚物薄膜结构及性能进行表征。结果表明:成功合成了PLA/PBAu嵌段共聚物,分子量可达10×10~4,玻璃化转变温度约为41℃;并且随着PBAu含量的增加,共聚物的结晶度逐渐增加。以NaOH溶液为模拟液进行加速降解实验发现,当PBAu含量为30%时,可以显著提高嵌段共聚物的降解速率,并且通过调节PLA、PBAu预聚物的含量,可以控制嵌段共聚物的降解速率。     

基于异氰酸酯衍生物的聚乳酸熔融扩链工艺、动力学及结构表征

以微波法氧化锌（ZnO）柱撑有机皂石催化丙交酯开环聚合的聚乳酸(PLA)为原料,分别采用二苯基甲烷二异氰酸酯 (MDI)和六亚甲基二异氰酸酯(HDI)进行熔融扩链反应,研究了扩链剂的用量和反应时间对PLA相对分子质量的影响,并对PLA的扩链动力学进行了研究。结果表明,最优的扩链反应工艺参数为：反应温度180 ℃,nNCO：nOH为2.5：1,MDI扩链时间为45 min,HDI扩链时间为30 min;MDI和HDI扩链反应的表观速率常数分别为6.081×10^3、6.98×10^3 g/(mol·min)。     

PLA/chain‐extended PEG blends with improved ductility

Melt blending of polylactic acid (PLA) and a chain‐extended polyethylene glycol (CE‐PEG) have been performed in an effort to toughen the PLA without significant loss of modulus and ultimate tensile strength. The chain‐extended PEG was prepared with melt condensation of a low molecular weight PEG and 4,4′‐methylenebis(phenylisocyanate) (MDI) for enhancement of the molecular weight of PEG. The thermal and mechanical properties, miscibility and phase morphologies of blends were investigated. By using thermal and fracture surface analysis, the blends were found to be a partially miscible system with shifted glass transition temperatures. The addition of CE‐PEG leads to slight decrease in tensile strength and modulus, while the elongation at break is characterized by an important increase (540%), compared with neat PLA and PLA/PEG (low molecular weight PEG, M_n = 35,000). The relative ductility of PLA/CE‐PEG is 40 times higher than that of neat PLA. The brittle fracture of neat PLA was transformed into a ductile fracture by the addition of CE‐PEG. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of Two‐Step Chain Extension using Joncryl and PMDA on the Rheological Properties of Poly (lactic acid)

This research considers a two‐step chain extension reaction in the presence of two chain extenders, Joncryl and Pyromellitic dianhydride (PMDA), as a solution for poor melt properties of poly (lactic acid) (PLA). The aim of adding PMDA is to increase the carboxyl groups via the anhydride ring‐opening reaction so that the reaction between PLA and Joncryl could be facilitated since the reactivity between the epoxy and carboxyl group is more than epoxy and hydroxyl group. The reactions are confirmed by measuring the acid value, and a two‐step reaction mechanism is suggested. Shear and elongational rheological properties of the samples are investigated; furthermore, gel permeation chromatography analyses and tensile tests are exploited for studying the molecular weight and tensile properties, respectively. The results show that the chain extension reactions lead to an increase in the storage modulus, complex viscosity, and molecular weight. Also, the PLA chains which are extended utilizing both chain extenders simultaneously evince a synergistic improvement in the shear and elongational rheological properties due to longer segments between branching points on the structure.     

Plasticized poly(lactic acid) with low molecular weight poly(ethylene glycol): Mechanical,thermal, and morphology properties

Poly(lactic acid) PLA was plasticized with low molecular weight poly(ethylene glycol) PEG‐200 to improve the ductility of PLA, while maintaining the plasticizer content at maximum 10 wt%. Low molecular weight of PEG enables increased miscibility with PLA and more efficient reduction of glass transition temperature (T_g). This effect is enhanced not only by the low molecular weight but also by its higher content. The tensile properties demonstrated that the addition of PEG‐200 to PLA led to an increase of elongation at break (>7000%), but a decrease of both tensile strength and tensile modulus. The plasticization of the PLA with PEG‐200 effectively lowers T_g as well as cold‐crystallization temperature, increasing with plasticizer content. SEM micrographs reveal plastic deformation and few long threads of a deformed material are discernible on the fracture surface. The use of low molecular weight PEG‐200 reduces the intermolecular force and increases the mobility of the polymeric chains, thereby improving the flexibility and plastic deformation of PLA. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4576–4580, 2013     

Synthesis and characterization of new optically active poly(amide‐imide‐urethane) thermoplastic elastomers,derived from 4,4′‐(hexafluoroisopropylidene)‐N,N′‐bis(phthaloyl‐L‐leucine‐p‐aminobenzoic acid) and PEG‐MDI

A new class of optically active poly(amide‐imide‐urethane) was synthesized via two‐step reactions. In the first step, 4,4′‐methylene‐bis(4‐phenylisocyanate) (MDI) reacts with several poly(ethylene glycols) (PEGs) such as PEG‐400, PEG‐600, PEG‐2000, PEG‐4000, and PEG‐6000 to produce the soft segment parts. On the other hand, 4,4′‐(hexafluoroisopropylidene)‐N,N′‐bis(phthaloyl‐L ‐leucine‐p‐amidobenzoic acid) (2) was prepared from the reaction of 4,4′‐(hexafluoroisopropylidene)‐N,N′‐bis(phthaloyl‐L ‐leucine) diacid chloride with p‐aminobenzoic acid to produce hard segment part. The chain extension of the above soft segment with the amide‐imide 2 is the second step to give a homologue series of poly(amide‐imide‐urethanes). The resulting polymers with moderate inherent viscosity of 0.29–1.38 dL/g are optically active and thermally stable. All of the above polymers were fully characterized by IR spectroscopy, elemental analyses, and specific rotation. Some structural characterization and physical properties of this new optically active poly(amide‐imide‐urethanes) are reported. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2288–2294, 2004     

A novel biodegradable multiblock poly(ester urethane) containing poly(l-lactic acid) and poly(butylene succinate) blocks

A novel biodegradable multiblock poly(ester urethane) (PEU), consisting of poly(l-lactic acid) (PLLA) and poly(butylene succinate) (PBS) blocks, has been successfully synthesized via chain-extension reaction of dihydroxyl terminated PLLA (PLLA-OH) and PBS prepolymers (PBS-OH) using toluene-2,4-diisocyanate (TDI) as a chain extender. The chemical structures and molecular weights of PEUs, containing different block lengths and weight fractions of PLLA and PBS, were characterized by ¹H NMR and GPC. The effects of the structures on the physical properties of PEUs were systematically studied by means of DSC, TGA, WAXD and tensile testing. The DSC results indicated that PLLA segment was compatible well with PBS segment in amorphous phase and the crystallization of PEU was predominantly caused by PBS segment, which was also confirmed by WAXD. The results of tensile testing showed that the extensibility of PLLA was largely improved by incorporating PBS segment. The PEU can be used as a potential substitute for some petroleum-based thermoplastics.     

Rapid synthesis of new block copolyurethanes derived from L‐leucine‐PEG in ionic liquids under microwave irradiation

This study concerns the synthesis of novel multi block polyurethane (PU) copolymers containing eco‐friendly segments, taking the advantage of ionic liquids (IL)s under microwave irradiation. For this, L ‐leucine anhydride cyclodipeptide (LAC) was prepared and then a new class of poly(ether‐urethane‐urea)s (PEUUs) was synthesized with two types of ILs, including room temperature imidazolium (RTIL)s and molten ammonium type ILs. ILs were used as reaction media and PUs were prepared via two‐step polymerization method. Polymerization reaction was also conducted under conventional heating method in N‐methyl pyrrolidone (NMP) as reaction solvent. In the first step, 4,4′‐methylene‐bis(4‐phenylisocyanate) (MDI) was reacted with LAC to produce isocyanate‐terminated poly(imide‐urea) oligomers as hard segment. Chain extension of the resulting prepolymer with polyethyleneglycol (PEG) of molecular weights of 400 (PEG‐400) was the second step to furnish a series of new PEUUs. These multiblock copolymers are optically active, thermally stable and soluble in amide‐type solvents. PEUUs prepared in ILs under microwave irradiation showed more phase separation and crystallinity than PEUU prepared under conventional method. Some structural characterization and physical properties of these PEUUs, prepared under different methods, are reported and compared. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of biodegradable lactic acid‐based polymers by chain extension

BACKGROUND: Poly(lactic acid) (PLA), coming from renewable resources, can be used to solve environmental problems. However, PLA has to have a relatively high molecular weight in order to have acceptable mechanical properties as required in many applications. Chain‐extension reaction is an effective method to raise the molecular weight of PLA. RESULTS: A high molecular weight biodegradable lactic acid polymer was successfully synthesized in two steps. First, the lactic acid monomer was oligomerized to low molecular weight hydroxyl‐terminated prepolymer; the molecular weight was then increased by chain extension using 1,6‐hexamethylene diisocyanate as the chain extender. The polymer was characterized using ¹H NMR analysis, gel permeation chromatography, differential scanning calorimetry and Fourier transform infrared spectroscopy. The results showed that the obtained polymer had a M_n of 27 500 g mol^?1 and a M_w of 116 900 g mol^?1 after 40 min of chain extension at 180 °C. The glass transition temperature (T_g) of the low molecular weight prepolymer was 47.8 °C. After chain extension, T_g increased to 53.2 °C. The mechanical and rheological properties of the obtained polymer were also investigated. CONCLUSION: The results suggest that high molecular weight PLA can be achieved by chain extension to meet conventional uses. Copyright © 2008 Society of Chemical Industry