用差减红外光谱分峰法测定乙丙齐聚物中端羟基的微结构

合成了端羟基乙丙齐聚物。用差减红外光谱对端羟基进行了分析。扣除了溶剂中三氯甲烷的干扰,用RUN.CAPR程序进行分峰,以正戊醇-1、3-甲基丁醇-1和丁醇-2为模型化合物标定伯、仲羟基吸收峰位置,并进行蜂面积积分,用模型化合物回归处理后得到定量公式:A=15.8667×10~3Cp+0.25674,以此求得乙丙齐聚物中伯、仲羟基的官能度。     

4-苯乙炔基苯胺封端聚酰亚胺树脂的合成与性能研究

使用4-苯乙炔基苯胺(4-PEA)作为反应性封端剂,和3,3′,4,4′-二苯醚四酸二酐(ODPA),3,3′,4,4′-联苯四酸二酐(BPDA),1,4-双(4′-氨基-2′-三氟甲基苯氧基)苯(BTPB)和3,4′-二氨基二苯醚(3,4-′ODA)反应合成了系列4-苯乙炔基苯基封端的聚酰亚胺低聚物,对低聚物的化学结构、热性能和熔体粘度以及固化后树脂的热性能等进行了研究.实验结果表明,低聚物均具有一定的结晶性,含有ODPA的聚酰亚胺低聚物较之含有BPDA的低聚物具有更低的熔体粘度,且出现最低熔体粘度的温度更低;固化后的树脂表现出良好的热性能,含有BPDA的树脂具有更高的玻璃化转变温度;系列低聚物中二胺单体的比例对于低聚物的熔体粘度和固化后树脂的热稳定性有一定影响.     

非异氰酸酯法合成脂肪族热塑性聚氨酯及其性能研究

利用二氨酯二醇氨酯交换的非异氰酸酯法合成高分子量的脂肪族热塑性聚氨酯.以己二氨酯二醇(BHCH)的自缩聚,合成了Mn为29200的聚己二氨酯(PBHCH),其熔点为154.31℃,拉伸强度为28.41MPa,断裂伸长率为3.91%;利用己内酰胺与乙醇胺的共聚合成了同时带有端氨基及端羟基的尼龙-6低聚物,并与己内酯反应转化为端羟基尼龙-6低聚体,经与BHCH在170℃常压反应4 h及180℃减压反应6.5 h,获得了数种带有短尼龙-6段的酰胺型聚氨酯(s-PAUs),红外、核磁、GPC、广角X-射线衍射、DSC、TGA和力学性能表征表明,此类s-PAUs的Mn在26000以上、熔点在123.85~170.89℃之间、拉伸强度达28.53 MPa、断裂伸长率达299.0%.     

氨基树脂交联型聚合物的合成及其取向松弛

用双羟基偶氮(或氧化偶氮)苯化合物与对苯二甲酰氯缩聚反应合成了端羟基偶氮(或氧化偶氮)苯低聚物。将其与丁醇醚化氨基树脂进行电场极化交联反应合成交联型非线性光学聚合物。利用红外光谱和紫外可见吸收光谱分别对交联反应、电场极化取向稳定性进行了研究。     

氨基树脂交联型聚合物的合成及其取向松驰

用双羟基偶氮苯化合物与对苯二甲酰氯缩聚反应合成了端羟基偶氮苯低聚物，将其与丁醇醚化氨基树脂进行电场极化交联反尖合成交联型非线性光学聚合物。利用红外光谱和紫外可见吸收光谱分别对交联反应、电场极化取向稳定性进行了研究。     

降冰片烯端基聚苯乙烯大分子单体的合成

近年来,大分子单体的合成及其共(自)聚合正日渐成为高分子合成中非常活跃的领域。本试验室曾合成了具有烯丙基端基的聚苯乙烯大分子单体(PS-allyl),并将其与乙烯、丙烯共聚合得到了乙丙共聚物(EPR)为主干、聚苯乙烯(PS)为支链的接校共聚物EPR-g-PS。本工作以5-溴甲基-2-降冰片烯(BrMNB)与聚苯乙烯阴离子(PS^-)偶合,制备具有降冰片烯端基的聚苯乙烯大分子单体(PS-NB)。     

共沸缩聚-解聚法高效合成乙交酯

乙交酯是聚羟基乙酸的单体,乙交酯的合成直接影响聚羟基乙酸的合成。一般用羟基乙酸(酯)制备乙交酯,但是,制备乙交酯的缩聚过程需要真空高温的条件,消耗大量的能量。共沸缩聚-解聚法制备乙交酯的缩聚过程,具有条件温和、无催化剂、溶剂可回收的优点。羟基乙酸通过共沸缩聚-解聚法得到乙交酯。用X-射线粉末衍射、红外分析、差热分析等方法对聚羟基乙酸低聚物进行了表征。结果表明：羟基乙酸制备的聚羟基乙酸低聚物是一种半结晶聚合物,聚羟基乙酸低聚物解聚得到产率为81.26%和纯度为89.29%的乙交酯,并且解聚反应残渣可以重复利用来制备乙交酯。     

4个天然1,7-二芳基庚烷类化合物的合成

合成了4个天然1,7-二芳基庚烷类化合物:1-(4′-羟基-3′-甲氧基苯基)-7-(4″-羟基苯基)-5-羟基-3-庚酮(1),1-(4′-羟基-3′-甲氧基苯基)-7-(4″-羟基苯基)-4-庚烯-3-酮(2),1-(3′,4′-二羟基苯基)-7-(4″-羟基苯基)-5-羟基-3-庚酮(3),1-(3′,4′-二羟基苯基)-7-(4″-羟基苯基)-4-庚烯-3-酮(4).化合物1,2,4为首次合成.     

MALDI-TOF质谱表征聚芳醚酮环状低聚物及其组分分布

应用介质辅助激光解吸离子化飞行时间质谱(MALDI-TOFMS),以二羟基苯甲酸为介质、N₂(337nm)为激光源,对两种聚芳醚酮环状低聚物的结构进行了确认,研究了环状低聚物不同聚合度组分的分布规律,并且与GPC质量分析法作了比较,实验结果表明,MALDI-TQF质谱是分析环状低聚物的准确、快速的工具之一.     

拒水型有机硅改性聚氨酯嵌段共聚物的合成与表征

以氨丙基硅氧烷偶联剂和端羟基聚二甲基硅氧烷(PDMS)为原料,合成了端氨丙基聚二甲基硅氧烷低聚物(SN2),并将其作为扩链剂,制备了有机硅-聚氨酯(Si-PU)嵌段共聚物.考察了聚氨酯预聚体的加料比(rNCO/OH)、SN2与聚氨酯预聚体的加料比(rNH2/NCO)对Si-PU嵌段共聚物溶液流变行为及其膜性能的影响.研究发现,该Si-PU共聚物的异丙醇溶液呈现较低的表观黏度及牛顿特性;成膜时,有机硅链段向表面迁移;膜表面对水的接触角达110°以上,且随着有机硅链段含量的增高而增大;共聚物膜的24 h吸水率较低(<1.5 wt%);但当有机硅链段含量过高时,吸水率反而增高.     

Functionality and Functionality Distribution Measurements of Binder Prepolymers

Abstract

The functionality of a prepolymer, which is defined as the ratio of molecular weight to equivalent weight, is probably the most important single parameter that determines the properties of the cross-linked polymer network. The determination of prepolymer functionality therefore requires accurate knowledge of both number average molecular weight and equivalent weight. Ideally, a suitable prepolymer for propellant binder applications has terminal functionality (OH or COOH). Such a prepolymer theoretically has a functionality of 2.0. Because of uncontrolled chain termination reactions during the prepolymer synthesis, however, not all polymer chains have the desired functional end group. As a result, prepolymers generally have a distribution of functionalities, including onfunctional, monofunctional, and the desired difunctional prepolymer.     

Novel synthesis of high‐molecular‐weight prepolymer of poly(p‐phenylene benzoxazole) in ionic liquids

Using ionic liquids (ILs) as the reaction solvent for the synthesis of prepolymer polyamide of poly(p‐phenylene benzoxazole) (PBO) was investigated. The optimum condition of prepolymer preparation was determined in ILs. A series of 1,3‐dialkylimidazolium ILs were used to be the reaction media of the polycondensation. The relationship between the molecular weight of prepolymer and the structure of ILs was analysed by changing the structure of the cation and species of anion of ILs. In order to prove the feasibility of the transformation, the prepolymer was used to prepare PBO in polyphosphoric acid media, and the conversion process was analyzed. The spinnability of the PBO solution was explored by the preparation of PBO fibers. The basic mechanical properties of PBO single fiber were tested. In a word, using 1,3‐dialkylimidazolium ILs as the reaction solvents was feasible for the synthesis of high‐molecular‐weight PBO prepolymer, which could be a promising PBO preparation method.     

Influence of molecular weight and free NCO content on the rheological properties of lithium lubricating greases modified with NCO-terminated prepolymers

In this work, the use of reactive diisocyanate-terminated polymeric materials as rheology modifiers of lubricating greases has been studied. Particularly, the influences that free NCO content, molecular weight and functionality of the reactive prepolymers exert on the rheological response and microstructure of lubricating greases were analyzed. With this aim, NCO-terminated prepolymers were prepared from several di and trifunctional polyols and polymeric MDI. Afterwards, the reaction between terminal isocyanate groups and the hydroxy group located in the hydrocarbon chain of the 12-hydroxystearate lithium soap, used as thickener, was promoted during processing of lubricating greases. Polymeric materials used as additives and final lubricating greases were characterized by FTIR, DSC and GPC techniques. The effectiveness of these reactive additives was tested by performing small-amplitude oscillatory shear (SAOS), as well as standardized mechanical stability tests, on final greases. The rheological response was related to the microstructure of these greases, characterized by means of atomic force microscopy (AFM). From the experimental results obtained, it may be concluded that the effectiveness of these polymeric additives to modify the rheology of greases is due to the progress of the reaction between terminal isocyanate groups and the hydroxy group of lithium soap. However, a large dependence on both free NCO content and prepolymer molecular weight was found. Experimental results confirm that a balance between prepolymer molecular weight and NCO content is necessary to reach an optimal rheological modification of lithium greases. Moreover, this balance is a function of grease ageing, due to the progress of the reaction promoted.     

Effect of prepolymer molecular weight on solid state polymerization of poly(bisphenol a carbonate) with nitrogen as a sweep fluid

The effect of prepolymer molecular weight on the solid‐state polymerization (SSP) of poly(bisphenol A carbonate) was investigated using nitrogen (N₂) as a sweep fluid. Prepolymers with different number–average molecular weights, 3800 and 2400 g/mol, were synthesized using melt transesterification. SSP of the two prepolymers then was carried out at reaction temperatures in the range 120–190 °C, with a prepolymer particle size in the range 20–45 μm and a N₂ flow rate of 1600 mL/min. The glass transition temperature (T_g), number–average molecular weight (M_n), and percent crystallinity were measured at various times during each SSP. The phenyl‐to‐phenolic end‐group ratio of the prepolymers and the solid‐state synthesized polymers was determined using 125.76 MHz ¹³C and 500.13 MHz ¹H nuclear magnetic resonance (NMR) spectroscopy. At each reaction temperature, SSP of the higher‐molecular‐weight prepolymer (M_n = 3800 g/mol) always resulted in higher‐molecular‐weight polymers, compared with the polymers synthesized using the lower molecular weight prepolymer (M_n = 2400 g/mol). Both the crystallinity and the lamellar thickness of the polymers synthesized from the lower‐molecular‐weight prepolymer were significantly higher than for those synthesized from the higher‐molecular‐weight prepolymer. Higher crystallinity and lamellar thickness may lower the reaction rate by reducing chain‐end mobility, effectively reducing the rate constant for the reaction of end groups. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4959–4969, 2008     

Synthesis and characterization of biodegradable poly(L-aspartic acid-co-PEG)

The melt polycondensation reaction of the prepolymer prepared from N-(benzyloxycarbonyl)-L -aspartic acid anhydride (N-CBz-L -aspartic acid anhydride) and low molecular weight poly(ethylene glycol) (PEG) using titanium isopropoxide (TIP) as a catalyst produced the new biodegradable poly(L -aspartic acid-co-PEG). This new copolymer had pendant amine functional groups along the polymer backbone chain. The optimal reaction conditions for the preparation of the prepolymer were obtained by using a 0.12 mol % of p-toluenesulfonic acid with PEG 200 for 48 h. The weight-average molecular weight of the prepolymer increased from 1,290 to 31,700 upon melt polycondensation for 6 h at 130°C under vacuum using 0.5 wt % TIP as a catalyst. The synthesized monomer, prepolymer, and copolymer were characterized by FTIR, ¹H- and ¹³C-NMR, and UV spectrophotometers. Thermal properties of the prepolymer and the protected copolymer were measured by DSC. The glass transition temperature (T_g) of the prepolymer shifted to a significantly higher temperature with increasing molecular weight via melt polycondensation reaction, and no melting temperature was observed. The in vitro hydrolytic degradation of these poly(L -aspartic acid-co-PEG) was measured in terms of molecular weight loss at different times and pHs at 37°C. This pH-dependent molecular weight loss was due to a simple hydrolysis of the backbone ester linkages and was characterized by more rapid rates of hydrolysis at an alkaline pH. These new biodegradable poly(L -aspartic acid-co-PEG)s may have potential applications in the biomedical field. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2949–2959, 1998     

Preparation and characterization of biodegradable poly(lactic acid)‐ block‐poly(ε‐caprolactone) multiblock copolymer

Biodegradable copolymers of poly(lactic acid)‐block‐poly(ε‐caprolactone) (PLA‐b‐PCL) were successfully prepared by two steps. In the first step, lactic acid monomer is oligomerized to low molecular weight prepolymer and copolymerized with the (ε‐caprolactone) diol to prepolymer, and then the molecular weight is raised by joining prepolymer chains together using 1,6‐hexamethylene diisocyanate (HDI) as the chain extender. The polymer was carefully characterized by using ¹H‐NMR analysis, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). The results of ¹H‐NMR and TGA indicate PLA‐b‐PCL prepolymer with number average molecular weights (M_n) of 4000–6000 were obtained. When PCL‐diols are 10 wt%, copolymer is better for chain extension reaction to obtain the polymer with high molecular weight. After chain extension, the weight average molecular weight can reach 250,000 g/mol, as determined by GPC, when the molar ratio of –NCO to –OH was 3:1. DSC curve showed that the degree of crystallization of PLA–PCL copolymer was low, even became amorphous after chain extended reaction. The product exhibits superior mechanical properties with elongation at break above 297% that is much higher than that of PLA chain extended products. Copyright © 2009 John Wiley & Sons, Ltd.     

双端羟基预聚物扩链制备高分子量聚对二氧环己酮

以1,4-丁二醇(BD)为引发剂, 辛酸亚锡为催化剂, 引发对二氧环己酮(PDO)开环聚合, 得到双端羟基型聚对二氧环己酮预聚物, 再以六亚甲基二异氰酸酯(HDI)为扩链剂制备高分子量的聚对二氧环己酮. 采用核磁共振谱对预聚物和扩链产物的结构进行了确认, 并详细考察了各种因素对扩链反应的影响. 研究结果表明, 加入适量的HDI, 于150 ℃反应60 min, 扩链效率在预聚物基础上可提高52倍, 而扩链产物的粘均分子量可达到25.7×104 g/mol.     

Topological bonding formation between an ultra‐high molecular weight linear polymer and a prepolymer at an early stage of free‐radical crosslinking polymerization

The free‐radical crosslinking polymerization of diallyl adipate (DAA) was carried out in the presence of poly(benzyl methacrylate) (poly(BzMA)) as a chemically inactive polymer in order to clarify the topological bonding formation between linear polymer and prepolymer before gelation; we found by chance that even at an early stage of the polymerization, the topological bonding was formed between ultra‐high molecular weight poly(BzMA) and poly(DAA) prepolymer.     

Detailed analysis of α,ω-bis(4-hydroxybutyl) poly(dimethylsiloxane) using GPC-MALDI TOF mass spectrometry

In this study the prepolymer alpha,omega-bis(4-hydroxybutyl) poly(dimethylsiloxane), used in the formulation of oxygen permeable films, is evaluated by gel permeation chromatography (GPC) combined with matrix assisted laser desorption ionization (MALDI) time of flight (TOF) mass spectrometry (MS). Two unexpected mass distributions are observed in the mass spectra. Reaction schemes for the formation of these distributions are proposed. A solution phase trimethylsilane end group modification was performed on the prepolymer to determine whether the unexpected mass distributions occur as impurities from synthesis or as artifacts from the MS process. Evaluation of the TMS modified prepolymer indicates the unexpected mass distributions indeed occur as impurities from the synthetic procedure. Average molecular weight values are determined by traditional GPC, direct MALDI-TOF MS, and GPC-MALDI-TOF MS methods and the results are compared.     

Synthesis of poly(urethane‐imide) using aromatic secondary amine‐blocked polyurethane prepolymer

A set of poly(urethane‐imide)s were prepared using blocked Polyurethane (PU) prepolymer and pyromellitic dianhydride (PMDA). The PU prepolymer was prepared by the reaction of polyether glycol and 2,4‐tolylene diisocyanate, and end capped with N‐methyl aniline. The PU prepolymer was reacted with PMDA until the evolution of carbon dioxide ceased. The effect of tertiary amine catalysts, organo tin catalysts, solvents, and reaction temperature were studied and compared with the poly(urethane‐imide) prepared using phenol‐blocked PU prepolymer. N‐methyl aniline blocked PU prepolymer gave a higher molecular weight poly(urethane‐imide) at a lower reaction temperature in a shorter time. Amine catalysts were found to be more efficient than organo tin catalysts. The reaction was favorable in particular with N‐ethylmorpholine and diazabicyclo(2.2.2)octane (DABCO) as catalysts, and dimethylpropylene urea as a reaction medium. The poly(urethane‐imide)s were characterized by FTIR, GPC, TGA, and DSC analyses. The molecular weight decreased with an increase in reaction temperature. The thermal stability of the PU was found to increase by the introduction of imide component. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4032–4037, 2000