熔融共聚法用外消旋乳酸直接合成聚乙醇酸-乳酸及其表征

以乙醇酸(GA)、廉价的外消旋乳酸(D,L-LA)为原料,以氯化亚锡(质量分数0.5％)为催化剂,在165℃、70 Pa下熔融聚合10 h,通过熔融共聚法直接合成了不同配比的系列生物降解材料聚乙醇酸-乳酸(PGLA),用凝胶渗透色谱、傅里叶变换红外光谱、核磁共振氢谱、差示扫描量热分析、X射线衍射等系统地对其进行了表征。当n(GA):n(D,L-LA)=1:1,直接熔融聚合法获得的D,L-PGLA 50／50的重均相对分子质量为24 300,比相同条件下合成的L-PGLA 50／50的18 000要高。     

药物缓释用生物降解材料聚乳酸-乙醇酸的合成

以D,L 乳酸、乙醇酸为原料,通过熔融聚合法直接合成生物降解材料聚乳酸 乙醇酸(PLGA)。在165℃、70Pa下熔融聚合10h,以w(SnCl2)=0 5%的氯化亚锡为催化剂时,特性黏数[η]最高可达0 2382dL/g。当使用人体营养添加剂如乳酸锌、乳酸钙、乙酸锌、硫酸锌、牛磺酸等作为无毒催化剂反应时,[η]为0 1036～0 2150dL/g。金属Lewis酸型催化剂乳酸锌与质子酸型催化剂牛磺酸复合使用,[η]为0 1068～0 1357dL/g,比牛磺酸催化时(0 1036dL/g)高,比乳酸锌催化时(0 1507dL/g)低,未见明显的协同效果。简单易行的直接熔融聚合法,尤其是用无毒催化剂催化合成,有利于拓展PLGA在药物缓释领域的应用。     

生物降解材料PLGA50的直接法合成与表征

分别以外消旋乳酸(D,L-LA)和左旋乳酸(L-LA)为原料,通过与乙醇酸(GA)熔融共聚[n(GA):n(LA)=1:1],直接合成了生物降解材料聚(乳酸-乙醇酸)(PLGA50)。用特性黏度[鏬、凝胶渗透色谱(GPC)、傅立叶红外光谱(FTIR)、核磁共振氢谱(1H　NMR)、差热分析(DSC)、X-射线衍射、接触角测试等手段,对PLGA50的相对分子质量、结构、性能等进行了系统的表征。PLGA50为无定型高分子,相同合成条件下D,L-PLGA50的相对分子质量比L-PLGA50高,其亲水性能比外消旋聚乳酸(PDLLA)有所改善。     

医用纤维材料PGLA910的直接熔融聚合法研究

分别以D,L-乳酸(D,L-LA)、L-乳酸(L-LA)为原料,与乙醇酸(GA)通过熔融聚合法进行共聚,在催化剂SnCl2用量0.5％(wt)、反应温度165℃、反应压力70Pa、反应时间10h的条件下直接合成了生物降解的医用纤维材料聚乙醇酸-乳酸(90/10)(PGLA 910)。产品用IR、DSC、X-射线衍射等进行了表征,并与乙交酯开环聚合二步法合成的PGLA910进行了比较。直接熔融聚合产品的结晶度接近于二步法,D,L-PGLA910的结晶度和微晶尺寸比L型的大。直接熔融共聚工艺流程短、简单易行、耗时少、成本低,有利于医用纤维材料PGLA910的规模开发。     

聚乳酸-己内酯直接熔融聚合工艺的研究

应用正交实验及SPSS统计软件研究聚乳酸-己内酯直接熔融聚合工艺。结果表明,质量分数 0．5％氯化亚锡为催化剂,乳酸与己内酯摩尔比为3/7,外消旋乳酸和左消旋乳酸与己内酯在180℃、70 Pa下分别直接熔融共聚12 h和16 h,可获得特性粘数分别为0．473 3 dL/g和0．412 1 dL/g的聚乳酸-己内酯。     

催化剂对L-乳酸和乙醇酸共聚物结构性能的影响

以L-乳酸(LA)和乙醇酸(GA)(LA:GA摩尔比为20:80)为原料,在170℃、压力小于70 Pa下反应10 h,直接熔融聚合合成乳酸-乙醇酸共聚物(PLGA),研究了催化剂种类、催化剂用量以及复配催化剂比例对PLGA特性粘数的影响。结果表明,使用复合催化剂氯化亚锡(SnC l2)与对甲基苯磺酸(TSA),摩尔比为1:1,其中SnC l2相对LA与GA的总质量的质量分数为0.4%时,所得PLGA产物的特性粘数较高,为0.352 dL/g。红外光谱和核磁共振氢谱表明,PLGA为LA与GA共聚物,共聚产物中GA比例大于投料值,由差示扫描量热分析和X射线衍射分析表明,PLGA为非结晶高聚物。     

基于熔融/固相缩聚制备中高分子量聚乙醇酸

聚乙醇酸（PGA）通常可通过乙交酯开环聚合和乙醇酸熔融缩聚制得,但乙交酯开环聚合工艺复杂,导致PGA成本高。相较而言,乙醇酸熔融缩聚制备PGA工艺简单,成本较低,但难以获得中高分子量的PGA。因此,本文基于熔融/固相缩聚路线,系统研究了催化剂种类与含量、酯化温度、固相缩聚温度等聚合工艺条件对PGA外观形态、特性黏度和热稳定性的影响。发现三氟甲烷磺酸铋对乙醇酸熔融缩聚具有较好的催化效果,优化熔融/固相缩聚条件如下：催化剂含量为0.20%（质量）,酯化温度为180℃,熔融缩聚和固相缩聚温度为210℃,固相缩聚时间为12 h。在该熔融缩聚条件下,PGA的最高特性黏度为0.36 dl/g,进一步固相缩聚处理可以将PGA的特性黏度提高到0.59 dl/g。     

正交试验法探讨聚乳酸直接熔融聚合工艺(英文)

通过正交试验探讨了聚乳酸直接熔融聚合工艺的最佳条件 ,即催化剂SnCl2 用量 0 .5 % ,反应温度180℃ ,反应压力 70Pa ,反应时间 10h。在上述条件下 ,分别以D ,L -乳酸和L -乳酸的单体为原料 ,可得粘均相对分子质量为 410 0的外消旋聚乳酸 (PDLLA) ,以及粘均相对分子质量近 10 0 0 0的聚左旋乳酸(PLLA)。与通常使用高沸点溶剂和特殊装置进行共沸脱水的聚乳酸直接溶液聚合工艺相比 ,直接熔融聚合法设备和工艺简单 ,试剂用量少 ,产品的合成周期短 ,提纯方便 ,成本更低 ,在聚乳酸生物降解材料的开发方面更具有优势     

直接熔融聚合聚乙醇酸的合成与表征

以乙醇酸为原料,在催化剂氯化亚锡质量分数0.5％,反应温度165℃,反应压力70 Pa,反应时间10 h的条件下进行熔融聚合,直接合成了生物降解的医用纤维材料聚乙醇酸(PGA),用IR,DSC,X射线衍射等进行了表征,并与乙交酯开环聚合二步法合成PGA进行了比较。直接熔融聚合PGA的结晶度和微晶尺寸高于二步法,其合成工艺流程短、简单易行、耗时少,有利于降低医用纤维材料PGA的开发成本。     

新型生物降解材料--含氢键聚乳酸的制备

采用熔融固相聚合制备了乳酸-氨基酸共聚物。结果表明：熔融聚合的最佳工艺条件为，催化剂是实验室制备，用量为0．5％～1％、聚合时间为10h、氨基酸含量为0．5％～1％；固相聚合的工艺条件为，聚合时间20h、催化剂为实验室制备。此工艺条件可制得相对分子质量大于50000的共聚物。     

Preparation and characterization of materials in the system xCuO-(50-x) CdO-50B2O3

New glassy materials in the system xCuO-(50-x) CdO–50B₂O₃ were prepared by a melting-quench technique. Their UV–vis, FTIR, electrical, dielectric, SEM, XRD patterns and density properties were investigated. SEM and XRD studies confirmed their amorphous nature and the presence of crystalline phases in the sample with 50 mol% CuO. Replacing CdO with increasing concentrations of CuO decreased the density and increased the molar volume. Optical reflectance spectra revealed the presence of Cu²⁺ ions in octahedral coordination, as well as the presence of Cu¹⁺ and Cuº in the samples with greater than 30% CuO. FTIR measurements confirmed the conversion of BO₄ units to BO₃ units with increasing CuO contents. The conduction in the CuO-containing samples increased as the CdO was completely replaced by CuO. The CuO-containing samples exhibited a slight increase in the ɛʹ values with increasing temperature and a decrease with increasing frequency. The ɛʹ values gradually increase upon replacing CdO with up to 40 mol% CuO. An abrupt increase in ɛʹ was recorded for the sample with 50 mol% CuO, particularly at high temperature. The latter sample showed an εʹ value of 927at 100 Hz and 298 K. Prepared samples with high ɛʹ values are promising candidates for capacitor materials in electronic devices.     

Comparison of the enthalpic relaxation of poly(lactide–co‐glycolide) 50:50 nanospheres and raw polymer

The phenomenon of enthalpic relaxation was evaluated for poly(lactide‐co‐glycolide) (PLGA, 50:50), in terms of storage of nanospheres for use as a controlled drug delivery system. Samples were stored for different times and temperatures below the glass transition temperature (T_g). Relaxation occurred at a significant rate up to 15 degrees below the T_g of 39.2°C. The effect of polymer morphology was considered by comparing the relaxation kinetics of the raw polymer with that of nanospheres formed using a novel technique. The nanospheres were shown to have a larger change in heat capacity at the glass transition and a longer average relaxation time than that of the raw polymer, and the relationship between these two parameters was discussed. For both the raw polymer and the nanospheres, relaxation was found to occur at a significant rate at room temperature. The storage of this system at subambient temperatures was therefore deemed important for maintaining the physicochemical properties of the system. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1868–1872, 2002     

50kt/a工业级磷酸一铵装置技术

以湿法磷酸与气氨为原料设计了一套50 kt/a采用连续法生产工业级磷酸一铵的生产装置。介绍其工艺流程、控制指标、主要设备选型、设备布置及吊装等技术,对肥料级磷酸一铵生产企业调整产品结构有一定意义。     

Effect of hydrolytic degradation and dehydration on the microstructure of 50:50 poly(glycolide-co-D,L-lactide)

The effect of hydrolytic degradation on the microstructure of unoriented, random 50: 50 poly(glycolic acid-co-D ,L -lactic acid) was examined using simultaneous small and wide angle X-ray scattering (SAXS/WAXS) and differential scanning calorimetry (DSC). Samples were degraded in phosphate-buffered saline solution at 37·5°C and studied wet and after dehydration. There was no evidence of crystalline material within the sample at any stage of degradation or dehydration from either X-ray scattering or thermal analysis. Thus, chain scission does not enable crystallization of the copolymer, and the glycolic acid and lactic acid fragments formed on degradation do not crystallize, even when the samples are dehydrated. Because such fragments are clearly formed (Hakkarainen, M., Albertsson, A. C. & Karlsson, S., Polym. Deg. Stab., 52 (1996) 283), and because they are crystalline in the dry state, it must be assumed either that these species are not present in any quantity in the degrading sample and that they diffuse easily from the bulk into the surrounding medium, or that the bulk polymer prevents them from crystallizing. SAXS gave evidence of small voids within the structure. Unlike dehydrated degraded semi-crystalline samples, there is no evidence for voiding on a macroscopic scale. The number and size of the small voids in the dehydrated samples rises with degradation. The voids close as samples are heated above the glass transition temperature and the amorphous chains gain mobility. The glass transition, although clearly visible in the undegraded samples, becomes less visible by DSC on degradation. After 28 days’ degradation, there is some evidence that the structure begins to close up, perhaps as a result of reduced viscosity arising from the increased fraction of low molecular weight material. © 1998 SCI.     

Dielectric properties and ferroelectric behavior of poly(vinylidene fluoride‐trifluoroethylene) 50/50 copolymer ultrathin films

Ultrathin films of poly(vinylidene fluoride‐trifluoroethylene) copolymer [P(VDF‐TrFE), with a content (mol %) ratio of 50/50 VDF/TrFE] were fabricated on silicon wafers covered with platinum by a spin‐coating technique, ranging in thickness from 20 nm to 1 μm. The effect of thickness on dielectric properties and polarization behavior was investigated. A critical thickness was found to be about 0.1 μm. An abrupt drop of dielectric constant was observed, although there is no significant change in dielectric loss at this thickness. Square and symmetric hysteresis loops were obtained in films thicker than 0.1 μm. However, for films thinner than 0.1 μm, fewer square hysteresis loops were observed. SEM and X‐ray results demonstrate that the effect of thickness on dielectric and ferroelectric properties could be explained by the changes of crystal structure in these films. In addition, the effects of irradiation on dielectric property and polarization response for ultrathin P(VDF‐TrFE) films were also presented. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2259–2266, 2001     

反相高效液相色谱法测定50%六氢-1,3,5-三(2-羟乙基)均三嗪

采用反相高效液相色谱法测定六氢-1,3,5-三(2-羟乙基)均三嗪,使用ZORBAX Extend-C18(250mm×4.6mm,5μm)色谱柱,以0.2%三乙胺水溶液-甲醇作为流动相,检测波长230nm,外标法对六氢-1,3,5-三(2-羟乙基)均三嗪进行分析和定量。方法的线性相关系数为0.9995,标准偏差为0.14%,变异系数为0.26%,平均回收率为99.9%。     

Tribological properties of SiO2 nanoparticle filled–phthalazine ether sulfone/phthalazine ether ketone (50/50 mol %) copolymer composites

SiO₂ nanoparticle filled–poly(phthalazine ether sulfone ketone) (PPESK) composites with various filler volume fractions were made by heating compression molding. The tribological behavior of the PPESK composites was investigated using a block‐on‐ring test rig by sliding PPESK‐based composite blocks against a mild carbon steel ring. The morphologies of the worn composite surfaces, wear debris, and the transferred films formed on the counterpart steel surface were examined with a scanning electron microscope, whereas the chemical state of the Fe element in the transfer film was analyzed with X‐ray photoelectron spectroscopy. In addition, IR spectra were taken to characterize the structure of wear debris and PPESK composites. It was found that SiO₂ nanoparticle filled–PPESK composites exhibit good wear resistance and friction‐reduction behavior. The friction and wear behavior of the composites was improved at a volume fraction between 4.2 and 14.5 vol % of the filler SiO₂. The results based on combined SEM, XPS, and IR techniques indicate that SiO₂ nanoparticle filled–PPESK composite is characterized by slight scuffing in dry sliding against steel and polishing action between composite surface and that of the countpart ring, whereas unfilled PPESK is characterized by severe plastic deformation and adhesion wear. In the former case a thin, but not complete, transfer film was formed on the surface of the counterpart steel, whereas in the latter case, a thick and lumpy transfer film was formed on the counterpart steel surface. This accounts for the different friction and wear behavior of unfilled PPESK and SiO₂ nanoparticle filled–PPESK composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2136–2144, 2002     

四官能度过氧化物JWEB50引发的PS-b-PMMA合成与表征

引言嵌段共聚物是具有两种或两种以上不同链段的聚合物,不同链段间存在的化学键限制了聚合物的相分离程度,易形成微相分离结构[1],而嵌段共聚物能作为聚合物共混体系的相容剂,只需加入少量