乳酸/聚乙二醇嵌段共聚物的合成与表征

利用直接缩聚法制备了乳酸与聚乙二醇的嵌段共聚物(PLEG)。采用正交试验法考察了乳酸与聚乙二醇质量比、催化剂种类、催化剂含量、反应温度和反应时间对PLEG性能的影响。结果显示优化的反应条件:乳酸与聚乙二醇质量比为8.5∶1.5,采用自制的复合催化剂,催化剂质量分数0.6%,聚合温度160℃,聚合时间5h。另外还考察了扩链剂对PLEG性能的影响,结果表明扩链剂能够显著提高PLEG的相对分子质量。对合成的PLEG通过红外光谱、核磁共振、热分析进行了表征。     

直接熔融聚合法合成生物降解材料PLEG研究 V反应机理

直接以乳酸(LA)单体和聚乙二醇(PEG)为原料,通过直接熔融共聚法,合成了生物降解材料聚乳酸-聚乙二醇(PLEG),用特性粘数[η]、GPC、FTIR1、H NMR、DSC和X-射线衍射等手段对其进行了系统的表征,发现许多因素对PLEG存在一定的影响,如不同的预聚方式时PLEG的组成不同、左旋乳酸(L-LA)获得的共聚物相对分子质量不如外消旋乳酸(D,L-LA)等。在此基础上,初步探讨了LA与PEG直接熔融共聚的反应机理。     

γ辐射硅橡胶固相接枝甲基丙烯酸甲酯的研究

利用60Coγ射线,研究了硅橡胶(SR)与甲基丙烯酸甲酯(MMA)固相接枝反应,考察了接枝单体浓度、辐射剂量和剂量率等因素对接枝反应的影响,用红外光谱(FT-IR)、热重分析(TG)、和接触角测定仪等分析手段对接枝产物的结构和性能进行了表征分析。实验结果表明:辐射剂量和单体浓度分别为30kGy和m(MMA)/m(SR)=0.1左右时,接枝效果较好,接枝后的硅橡胶的热性能和亲水性能得到改善。     

核动力船舶EPDM密封件的寿命研究

重点研究了EPDM(三元乙丙橡胶)密封件的寿命。首先通过加速老化方法和Arrhenius定律研究了其在使用过程中的热老化行为,估算了其经过19 a和32 a老化后的力学性能变化。之后研究了不同剂量γ辐射对其性能的影响:高温加10 k Gy、20 k Gy和400 k Gy辐射,以及18 k Gy、33 k Gy和250 k Gy(仅辐射)。密封件都在热老化后进行辐射。测试了密封件表面及中部(断面10 mm×10 mm,直径68 mm)的力学性能(压缩力、拉伸强度和硬度)。另外还进行了热重分析(TGA)和差示扫描量热(DSC)分析。结果表明,在正常条件下使用32 a后,EPDM密封件的性能变化很小(压缩力变化20%,拉断伸长率变化30%)。另一方面,在250 k Gy及400 k Gy剂量下辐射后,密封件的性能变化很关键(压缩力+130%)。研究结果与其他有关该聚合物的研究结果相符,即辐射剂量250 k Gy可使其性能发生较大变化。     

电子束辐射对聚苯硫醚结构和性能的影响

研究了在室温下空气环境中电子束辐射聚苯硫醚过程中,不同辐射剂量对聚苯硫醚的表面化学结构、热性能和力学性能的影响。结果表明,在电子束辐射下,聚苯硫醚表面发生氧化,且氧含量随着辐射剂量的增大而升高。由于辐射所致结构变化,聚苯硫醚制件表面部分的结晶温度和熔点随着辐射剂量的增大呈现先升高后降低的趋势。然而,聚苯硫醚样品内部的元素组成、热性能和力学性能几乎不受辐射剂量的影响。     

不同投料比对直接熔融聚合法生物降解材料聚乳酸-聚乙二醇的影响

以氧化亚锡为催化剂(mc／mLA=0．005),以外消旋乳酸(D,L-LA)单体为原料,使其与数均相对分子质量为1000的聚乙二醇(PEG)共聚,通过直接熔融共聚法,在1650℃、70Pa下反应15h,合成了生物降解材料聚乳酸-聚乙二醇(PLEG)。发现最佳投料比为mu／mPEG=9时,可顺利地得到共聚产物PLEG,且其特性黏数[η]可达最高(0．4009dL/g),产物的亲水性能也得到改善,有利于PLEG作为药物缓释载体的应用。     

高密度聚乙烯电子束辐射交联的研究

用高能电子束辐射技术研究了添加敏化剂季戊四醇三丙烯酸酯(PETA)和抗氧剂300的高密度聚乙烯(HDPE)体系的辐射交联效应.通过测定试样辐射后交联度、拉伸强度、直角撕裂强度等性能,考察了辐射剂量、w(PETA)和 w(300)对 HDPE辐射交联的影响;并用差示扫描量热法和热重分析研究了HDPE辐射后的结晶性和热稳定...     

乳酸与聚乙二醇熔融聚合及表征

以L-乳酸与聚乙二醇为原料,熔融共聚,再固相聚合得到聚乳酸-聚乙二醇共聚物(PLEG)。用凝胶渗透色谱(GPC)、红外光谱(FTIR)、熔点测试、差示扫描量热法(DSC)、吸湿率测试等手段对其进行表征,发现相同条件下,聚乳酸-聚乙二醇共聚物吸湿率高于聚乳酸。     

直接熔融聚合法合成生物降解材料PLEG研究Ⅳ预聚方式的影响

直接以乳酸(LA)单体和聚乙二醇(PEG)为原料,通过直接熔融共聚法,合成了生物降解材料聚乳酸-聚乙二醇(PLEG),用特性粘数[η]、GPC、FTIR、1H NMR、DSC等手段对其进行了系统的表征,发现不同的预聚方式存在一定的影响,LA和PEG直接进行一步预聚时相对分子质量较高,对药物缓释载体PLEG的合成较为有利.     

电子束辐射改性无卤阻燃聚烯烃复合材料的性能研究

利用高能电子束辐射技术,对以乙烯-辛烯共聚物(POE)/线型低密度聚乙烯(LLDPE)为基体树脂,无机氢氧化铝(ATH)/微胶囊包覆红磷(MRP)为阻燃剂,三烯丙基异氰脲酸酯(TAIC)为交联助剂所制备的无卤阻燃复合材料进行了辐射改性研究。通过热性能、动态热机械分析、低场核磁交联密度仪、断面微观形貌及介电性能的测试,研究了辐射剂量的变化对于POE/LLDPE/ATH/MRP阻燃材料的性能和交联程度的影响。结果表明:随着辐照剂量的增加,其交联密度由小变大,而后由大再变小,分子链的受束缚程度显示出先增强后减弱的趋势,当辐照剂量为150 k Gy左右时,材料的交联密度最大及玻璃化转变温度(Tg)最高;同时拉伸强度从辐照前的7.72 MPa上升至9.14 MPa,高温热稳定性得到提高;介电常数随着辐射剂量的增加而呈先上升后下降的趋势,电子束辐射对介电损耗的影响甚微。     

Degradation of poly(D,L‐lactic acid)‐b‐poly(ethylene glycol) copolymer and poly(L‐lactic acid) by electron beam irradiation

This article investigated the effects of electron beam (EB) irradiation on poly(D ,L ‐lactic acid)‐b‐poly(ethylene glycol) copolymer (PLEG) and poly(L ‐lactic acid) (PLLA). The dominant effect of EB irradiation on both PLEG and PLLA was chain scission. With increasing dose, recombination reactions or partial crosslinking of PLEG can occur in addition to chain scission, but there was no obvious crosslinking for PLLA at doses below 200 kGy. The chain scission degree of irradiated PLEG and PLLA was calculated to be 0.213 and 0.403, respectively. The linear relationships were also established between the decrease in molecular weight with increasing dose. Elongation at break of the irradiated PLEG and PLLA decreased significantly, whereas the tensile strength and glass transition temperature of PLLA decreased much more significantly compared with PLEG. The presence of poly(ethylene glycol) (PEG) chain segment in PLEG was the key factor in its greater stability to EB irradiation compared with PLLA. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Formation of honeycomb films from poly(L‐lactide)‐block‐poly(ethylene glycol) via water‐droplet templating

The fabrication of honeycomb‐patterned films from amphiphilic poly(L ‐lactide)‐block‐poly(ethylene glycol) (PLEG) in a high‐humidity atmosphere is reported. The influence of the solution concentration on pattern formation was investigated. Moreover, by comparing the different conditions of fabricating regular structures between PLEG and poly(phenylene oxide), the mechanism of the regular pattern formation was studied. Finally, by adding sodium dodecylsulfate to a concentrated solution of 1 g L^?1 PLEG? CHCl₃ which otherwise could not form regular pores, we found that regular pores could be obtained. The PLEG honeycomb films are expected to be of use in cell culture, tissue engineering and many other areas. Copyright © 2007 Society of Chemical Industry     

Influence of experimental parameters and the copolymer structure on the size control of nanospheres in double emulsion method

Poly(lactide-ethylene glycol) (PLEG) and poly(lactide-methoxy poly(ethylene glycol)) (MePLEG) nanospheres used as drug carrier were prepared by a double emulsion method. The influences of several parameters, such as copolymer structure, phase volume ratios, emulsifer concentration and sonication parameters, on the preparation of these two copolymer nanospheres were investigated for the nanospheres control. Critical values of the emulsifer concentration and the sonication intensity exist, allowing optimization of the nanospheres of controlled size with a narrow distribution. Under the same condition, MePLEG nanospheres had a smaller size than PLEG nanospheres because of their different length of hydrophilic blocks and steric hindrance. In addition, vascular endothelial cell growth factor and cisplatin, as two water-soluble model drugs, were encapsulated in the MePLEG and PLEG nanospheres. A higher encapsulation efficiency, above 90%, of the PLEG nanospheres could be obtained than that of the MePLEG nanospheres because of their different hydrophilic blocks structure.     

Syntheses of poly(lactic acid)‐poly(ethylene glycol) serial biodegradable polymer materials via direct melt polycondensation and their characterization

Directly starting from lactic acid (LA) and poly(ethylene glycol) (PEG), biodegradable material polylactic acid‐polyethylene glycol (PLEG) was synthesized via melt copolycondensation. The optimal synthetic conditions, including prepolymerization method, catalyst kinds and quantity, copolymerization temperature and time, LA stereochemical configuration, feed weight ratio m_LA/m_PEG and M_n of PEG, were all discussed in detail. When D ,L ‐LA and PEG (M_n = 1000 Da) prepolymerized together as feed weight ratio m_{D ,l‐LA}/m_PEG = 90/10, 15 h copolycondensation under 165°C and 70 Pa, and 0.5 wt % SnO as catalyst, gave D ,L ‐PLEG1000 with the highest [η] of 0.40 dL/g, and the corresponding MW was 41,700 Da. Using L ‐LA instead of D ,L ‐LA, 10 h polymerization under 165°C and 70 Pa, and 0.5 wt % SnO as catalyst, gave L ‐PLEG1000 with the highest [η] of 0.21 dL/g and MW of 15,600 Da. Serial D ,L ‐PLEG with different feed weight ratio and M_n of PEG were synthesized via the simple and practical direct melt copolycondensation, and characterized with FTIR, ¹H NMR, GPC, DSC, XRD, and contact angle testing. D ,L ‐PELG not only had higher MW than PDLLA, PLLA and L ‐PELG, but also better hydrophilicity than PDLLA. The novel one‐step method could be an alternative route to the synthesis of hydrophilic drug delivery carrier PLEG instead of the traditional two‐step method using lactide as intermediate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 577–587, 2006     

马来酸酐改性端羟基乳酸预聚体的合成及性能研究

采用聚乙二醇（PEG）与乳酸反应,合成了端羟基乳酸预聚体（PLEG）。然后将PLEG与马来酸酐进行直接熔融缩聚得到改性聚乳酸（MPLA）。采用正交分析法探讨了原料比、反应温度、反应时间等工艺条件对MPLA相对分子质量的影响,并研究了MPLA的亲水性能、力学性能和在体外模拟生物环境中的降解特性。结果表明：马来酸酐与PLEG的质量比为1:15,在130 ℃反应15 h,MPLA的黏均相对分子质量最大为61564。相较于PLEG,MPLA的拉伸强度、弹性模量和断裂伸长率明显提高,亲水性得到改善。MPLA在体外模拟生物环境中的降解性能较好,其降解速率与马来酸酐含量有关。     

Thermal,structural, and optical properties of γ‐irradiated poly(vinyl alcohol)/poly(ethylene glycol) thin film

Poly(vinyl alcohol)/poly(ethylene glycol) (PVA/PEG) copolymer was prepared using casting technique. The obtained PVA/PEG thin films have been irradiated with gamma rays with doses ranging from 1.5 to 20 Gy. The resultant effect of gamma irradiation on the thermal properties of PVA/PEG has been investigated using thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The onset temperature of decomposition T_o and activation energy of thermal decomposition E_a were calculated, results indicating that the PVA/PEG thin film decomposes in one main weight loss stage. Also, the gamma irradiation in dose range 4–12 Gy led to a more compact structure of PVA/PEG copolymer, which resulted in an improvement in its thermal stability with an increase in the activation energy of thermal decomposition. The variation of transition temperatures with gamma dose has been determined using DTA. The PVA/PEG thermograms were characterized by the appearance of an endothermic peak due to melting of crystalline phase. In addition, structural property studies using X‐ray diffraction and infrared spectroscopy were performed on both nonirradiated and irradiated samples. Furthermore, the transmission of the PVA/PEG samples and any color changes were studied. The color intensity (E was greatly increased with increasing the gamma dose and was accompanied by a significant increase in the blue and green color components. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Study of a Polydimethylsiloxane (PDMS) Elastomer Generated by γ Irradiation: Correlation Between Properties (Thermal and Mechanical) and Structure (Crosslink Density Value)

The present study investigates the structural modification of polydimethylsiloxane (PDMS) with a molecular weight of 35 kDa, using varying high doses of gamma irradiation. Elastomeric structures with different crosslinked density values were obtained as a function of the gamma irradiation dose (250, 300, 350 and 400 kGy). The structural characterization of the obtained elastomers was performed by employing Fourier Transform Infrared, ²⁹Si Magic Angle Spinning Nuclear Magnetic Resonance and X-Ray Diffraction (FTIR, ²⁹Si MAS NMR and XRD), showing integration with the polymer chains by siloxane crosslinks (Type-Y) and methylene crosslinks (Type-H). The mechanical and thermal characterizations were carried out by employing dynamical-mechanical analysis (DMA) and modulated differential scanning calorimetry (MDSC). The results showed an important correlation between the thermo-mechanical behavior and the irradiation dose. The thermal stability, analyzed by a thermo-gravimetric analysis (TGA), exhibited interesting behavior that suggested a direct correlation between the decomposition temperature and the structure generated by the gamma irradiation. These results suggest that the obtained elastomers could potentially be considered shape changing materials (SCM).     

Synergistic effect of short reinforced fibers and gamma rays on the thermal and mechanical properties of waste poly(propylene) composites

Compressed molded waste poly(propylene) was reinforced with short carbon and/or glass fibers for investigation. The prepared composites were γ‐irradiated to estimate the role of the ionizing radiation as a compatibilizing agent. TGA and DSC were used to investigate the influence of exposure dose and the incorporation of short fibers on the thermal parameters of the prepared composites. The mechanical properties of different composites were also studied. It was observed that the mechanical and thermal parameters were highly affected by the kind of incorporated fibers and γ‐irradiation. The structural and morphological studies were made by means of XRD and SEM to investigate the structure change caused by the incorporation of short fibers and exposure to γ‐irradiation. The results show that the irradiation of carbon fiber–containing composite magnified its thermal stability and its tensile strength. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1741–1747, 2005