稀土成核剂对聚乳酸非等温行为的影响

利用差示扫描量热仪(DSC)研究了3种稀土成核剂[WBG-Ⅱ、WBG-Ⅱ(a)与WBG-Ⅱ(b)]对聚乳酸(PLA)的影响。非等温结晶动力学分析表明:添加成核剂后在相同的降温速率下结晶发生的温度区间比纯PLA高11～15℃,其中WBG-Ⅱ(b)在10℃/min的降温速率下可以将PLA的结晶温度由109.2℃提高到124.1℃,结晶诱导时间tinc由8.43 min减少到6.55 min,说明可以作为1种有效的PLA成核剂。     

Morphology and Properties of Poly(L‐Lactide) (PLLA) Filled with Hollow Glass Beads

The morphology, crystalline behavior, and mechanical and thermal properties of poly(L ‐lactide)/hollow glass beads (PLLA/HGBs) composites were investigated. The incorporation of HGBs enhanced the crystallization rate and crystallinity of PLLA, but slightly decreased its elongation at break. In addition, HGBs acted as stress concentration points inducing the plastic deformation of PLLA, leading to increased Izod impact strength. Differential scanning calorimetry results show that annealed PLLA eliminated cold crystallization phenomenon in the region of 100–140 °C and presented a double melting peak around 150 °C. Moreover, annealing was demonstrated to be effective for the improvement of tensile modulus, strength, Izod impact strength and heat distortion temperature of the composites due to the increased crystallinity and more perfect crystals. Silane coupling agents can enhance the interfacial adhesion of the composites, and lead to better mechanical properties. Compared to neat PLLA, the HGBs filled PLLA composites did not exhibit an obvious increase of the density.

     

聚乙二醇改性聚乳酸幽门螺杆菌微球疫苗的制备与体外控释

目的 应用聚乳酸与聚乙二醇共聚物（ＰＥＬＡ）包裹Ｈｐ超声上清液,制备 Ｈｐ口服微球疫苗,探讨共 聚物ＰＥＬＡ总相对分子质量ｒ、ＰＥＧ含量与不同相对分子质量ＰＥＬＡ共聚物的相对分子质量分布（Ｍｒ／Ｍｎ）对微球疫 苗体外释药特性的影响。方法　采用复乳法溶剂挥发技术,制备Ｈｐ微球疫苗,用电子显微镜与扫描电镜观测微球 疫苗的粒径,用紫外光谱分光光度法测定抗原包裹效率与Ｈｐ抗原释放量,并在ｐＨ７．３、浓度为 ０．０１ｍｏｌ／Ｌ的ＰＢＳ溶 液中作体外控释实验。结果 Ｈｐ微球疫苗抗原包裹效率在７５％左右,平均粒径在５１μｍ以下。若ＰＥＧ量低于 １０％,ＰＥＬＡ组成对微球疫苗的粒径和抗原包裹效率影响不大。结论 Ｈｐ抗原体外释放量与 ＰＥＬＡ中ＰＥＧ的量和 相对分子质量、ＰＥＬＡ的相对分子质量分布成正比,而与ＰＥＬＡ的总相对分子质量成反比。     

Poly(L‐Lactide), 8. High‐Temperature Hydrolysis of Poly(L‐Lactide) Films with Different Crystallinities and Crystalline Thicknesses in Phosphate‐Buffered Solution

Poly(L ‐lactide) (PLLA) films having different crystallinities (X_c's) and crystalline thicknesses (L_c's) were prepared by annealing at different temperatures (T_a's) from the melt and their high‐temperature hydrolysis was investigated at 97°C in phosphate‐buffered solution. The changes in remaining weight, molecular weight distribution, and surface morphology of the PLLA films during hydrolysis revealed that their hydrolysis at the high temperature in phosphate‐buffered solution proceeds homogeneously along the film cross‐section mainly via the bulk erosion mechanism and that the hydrolysis takes place predominantly and randomly at the chains in the amorphous region. The remaining weight was higher for the PLLA films having high initial X_c when compared at the same hydrolysis time above 30 h. However, the difference in the hydrolysis rate between the initially amorphous and crystallized PLLA films at 97°C was smaller than that at 37°C, due to rapid crystallization of the initially amorphous PLLA film by exposure to crystallizable high temperature in phosphate‐buffered solution. The hydrolysis constant (k) values of the films at 97°C for the period of 0–8 h, 0.059–0.085 h^–1 (1.4–2.0 d^–1), were three orders of magnitude higher than those at 37°C for the period of 0–12 months, 2.2–3.4×10^–3 d^–1. The melting temperature (T_m) and X_c of the PLLA films decreased and increased, respectively, monotonously with hydrolysis time, excluding the initial increase in T_m for the PLLA films prepared at T_a = 100, 120, and 140°C in the first 8, 16, and 16 h, respectively. A specific peak that appeared at a low molecular weight around 1×10⁴ in the GPC spectra was ascribed to the component of one fold in the crystalline region. The relationship between T_m and L_c was found to be T_m (K) = 467·[1–1.61/L_c (nm)] for the PLLA films hydrolyzed at 97°C for 40 h.     

PLA复合材料降解性能研究进展

概述了聚乳酸(PLA)的降解理论,重点综述了PLA复合材料水解和热降解的国内外研究进展,并展望了PLA复合材料降解研究的发展方向。     

羟基磷灰石/聚乳酸复合材料制备的研究进展

聚乳酸是一类重要的生物降解聚合物,羟基磷灰石是人体骨骼的基本成分。以羟基磷灰石为增强材料、聚乳酸为基体制备的羟基磷灰石/聚乳酸复合材料,是无机/有机生物复合材料的典型代表,具有良好的力学性能与生物相容性,在很多领域有重要的应用。本文主要综述了羟基磷灰石/聚乳酸复合材料的制备方法。     

Optimization of Process Parameters for Controlled Ring-Opening Polymerization of Lactide to Produce Poly(L-Lactide) Diols as Precursor for Polyurethanes

Series of poly(L-Lactide) diols with molecular weights (M_n) in 2,069–4,811?g mol^?1 were synthesized from L-Lactide using stannous octoate catalyst and 1,4-butanediol chain extender. Operating conditions, i.e., temperature, catalyst concentration, chain extender concentration, and reaction time, were optimized. Maximum monomer conversion and M_n were observed at 0.5?mol% SnOct₂ and 1.0?mol% 1,4 butanediol (BDO) at 145°C. Poly(L-Lactide) diols were analyzed by Fourier transform infrared, proton nuclear magnetic resonance, end-group analysis, and X-ray diffraction techniques. Fourier transform infrared confirmed the formation of poly(L-Lactide) diols. Poly(L-Lactide) diols’ % degree of crystallinity was determined by X-ray diffraction. M_n was calculated by proton nuclear magnetic resonance and end-group analysis.     

Preparation and Characterization of Biological Non-toxic Hybrid Nanoparticles Based on Lactide and Poly(ethylene glycol) Loading Docetaxel for Anticancer Drug Delivery

Hybrid nanoparticles based on lactide and poly(ethylene glycol) were composed of a copolymer, poly(2-amino,1,3-propanediol carbonic ester-co-lactide) [P(LA-co-CA)], and a graft copolymer, poly(2-amino,1,3-propanediol carbonic ester-co-l-lactide)-g-methoxy-poly(ethylene glycol) [P(LA-co-CA)-mPEG]. The hybrid nanoparticles were prepared using emulsion solvent diffusion method. The copolymer of poly(2-benzyloxy amide,1,3-propanediol carbonic ester-co-lactide) was prepared using ring-opening polymerization with diethylzinc (ZnEt₂) as a catalyst, and then took off benzyl oxygen group to obtain P(LA-co-CA). P(LA-co-CA)-mPEG by grafting methoxy-PEG-propionaldehyde (mPEG-ALD) on P(LA-co-CA). With docetaxel as a model drug, the morphology of nanoparticles was characterized by scanning electron microscopy (SEM) and the size and size distribution were determined by dynamic light scattering (DLS). The size of DTX-loaded particle was approximately 110 nm. The size scale prevents them from uptake by the reticulo-endothelial system and accumulation at the target site through the enhanced permeability and retention effect. In MTT assay, the results showed that the polymers are non-cytotoxic. The study points to the potential application of the composite nanoparticles in biomedical applications, including tissue engineering and controlled drug delivery.     

Poly(ortho-vinylbenzophenone)

This article reports the synthesis and free radical polymerization of ortho-vinylbenzophenone. The glass transition temperature T_g of the homopolymer is 136°C. The products synthesized appeared to be atactic and amorphous. The Mark-Houwink constants for poly (o-vinylbenzophenone) in tetrahydrofuran are K = 4.2 × 10^?2 cm³ g^?1 and a = 0.765. The pre-exponential constant under theta conditions, K_θ, is estimated to be 5.93 × 10^?2 cm³ g^?1. The ratio of unperturbed dimensions of the actual polymer and free rotating analogue chain is 3.93, which is almost double that of polystyrene. The Flory-Huggins interaction parameter for poly $\text{(o-}\text{vinylbenzophenone}\text{)}\text{tetrahydrofuran}$ is 0.48 at room temperature. The $\text{k}{}_{\mathrm{<mtext>p</mtext>}}\text{k}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}_{\mathrm{<mtext>t</mtext>}}$ ratio at 60°C is $\text{1.1 × 10}{}^{\mathrm{?2}}\text{l}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{mol}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}\text{s}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}$. In free radical copolymerizations with styrene at 70°C, r₁ (o-vinylbenzophenone) = 1.216, r₂ = 0.751. This copolymerizations is virtually random.     

苯乙烯—异戊二烯—苯乙烯热塑性嵌段共聚物

简介近年来国外SIS生产状况、生产工艺技术经济评估、SIS的基本性能和应用以及国外技术发展趋势,井对国内SIS产品开发作出预估。     

Poly(alkylnylstannanes)

Summary The synthesis of poly(alkynylstannanes) was achieved by the step-growth polymerization of bisaminostannanes and ,-diynes. This is a new class of organotin polymers containing tin-alkyne linkages in the polymer backbone. The polymers were obtained in good yield, albeit with relatively low molecular weight. The polymers underwent crosslinking on standing to give insoluble material and required stabilization with radical inhibitors. The thermal properties of these materials, and the influence of the group pendent to tin are discussed.     

聚羟基烷酸酯改性聚氯乙烯的研究

通过熔融共混的方法分别制备了聚氯乙烯/邻苯二甲酸二辛酯/聚羟基烷酸酯（PVC/DOP/PHA）和PVC/PHA共混物。研究了PHA逐步代替DOP对共混物力学性能和熔体流动性能的影响规律,利用扫描电子显微镜对所制备的试样进行微观结构分析。结果表明,随着共混体系中PHA用量的增加和DOP的等量减少,与PVC/DOP共混物相比,PVC/DOP/PHA共混物的拉伸强度由21 MPa提高至42 MPa,断裂伸长率先增加而后降低,在PHA含量为10.7 %(质量分数,下同)时出现极大值(350 %);在PVC/PHA体系中,PHA含量增加,PVC/PHA共混物的力学性能及熔体流动速率都显著提高,说明PHA可以作为PVC的一种有效的绿色增塑剂和增韧剂。     

聚β-羟基丁酸酯和聚碳酸亚丙酯的共混体系研究

采用溶剂挥发法和熔融共混法分别制备了聚β-羟基丁酸酯(PHB)和聚碳酸亚丙酯(PPC)的共混物,采用DSC、X-射线衍射、扫描电镜、偏光显微镜等手段系统研究了共混物配比对体系热、力学性能、形貌的影响.结果表明,随着共混物中PHB含量的增加,共混物断裂强度增大,PPC的加入可明显改善材料脆性,断裂伸长率增大.PPC的存在可以抑制PHB的结晶过程,降低PHB的熔点,拓宽PHB的熔融加工窗口.上述共混物在可降解塑料领域具有良好的应用前景.     

Dispersion of Poly(phenylene ether) in a Poly(phenylene sulfide)/Poly(phenylene ether) Alloy

We have devised and developed a new method for the preparation of a poly(phenylene sulfide)/poly(phenylene ether) (PPS/PPE) alloy, which has micro‐dispersed PPE in the PPS matrix. PPS was chemically treated to activate the reactivity of the PPS end‐group by extrusion in the presence of diphenylmethane diisocyanate (MDI) in its molten state at 300°C. The reactive processing of the MDI‐treated PPS with maleic anhydride‐modified PPE gave a PPS/PPE alloy with micro‐dispersed PPE in the PPS matrix. The PPS/PPE alloy showed mechanical properties superior to those of PPS at elevated temperature (150°C) and also showed precision‐molding ability superior to that of PPS.     

Polaron Hopping in Nano-scale Poly(dA)–Poly(dT) DNA

We investigate the current–voltage relationship and the temperature-dependent conductance of nano-scale samples of poly(dA)–poly(dT) DNA molecules. A polaron hopping model has been used to calculate the I–V characteristic of nano-scale samples of DNA. This model agrees with the data for current versus voltage at temperatures greater than 100 K. The quantities G ₀ , i ₀ , and T _1d are determined empirically, and the conductivity is estimated for samples of poly(dA)–poly(dT).     

Branched Poly(ethyleneterephthalate)

Abstract

Several batches of branched poly(ethyleneterephthalate) (PET) of varying degrees of branching were prepared, using common PET monomers and special branching monomers synthesized by us. For the purpose of originality the trifunctional branch points currently employed by various industrial manufacturers were avoided and only tetra-, hexa- and octa-functional branching monomers were created and incorporated into the PET chains. The combination of intrinsic viscosity (I.V.) and light scattering measurements indicates that, as expected, higher functionality branchpoint monomers are more effective branching agents than their lower functionality analogues, and the molecular weight within each series of branched PET increases with increasing concentration of branching residues. Increasing amounts of microgels appear in the preparations as the concentration increases of effective branchpoint residues in the branched PET.     

Poly(methyl methacrylate-co-acrylonitrile)

Stable macroradicals of methyl methacrylate were prepared by the azobisisobutyronitrile-initiated polymerization of methyl methacrylate in hexane whose solubility parameter value (δ) differed from that of the macroradical by more than 1.8 hildebrand units and in 1-propanol at temperatures below its theta temperature (84.5°C). The rates of heterogeneous polymerization in hexane and 1-propanol were much faster than that of the homogeneous polymerization in benzene. Stable macroradicals were not obtained in benzene which was a good solvent nor at temperatures above the glass transition temperature (T_t) of the macroradicals. Thus, stable macroradicals of butyl methacrylate (T_g20°C) and and methyl acrylate (T_g3°C) were not obtained at a polymerization temperature of 50°C. Good yields of block copolymers of methyl methacrylate and acrylonitrile were obtained by the addition of acrylonitrile to the methyl methacrylate macroradical in methanol, ethanol, 1-propanol and hexane at 50°C. The rate of formation of the block copolymer decreased in these poor solvents as the differences between the solubility parameter of the solvent and macroradical increased.The block copolymer samples prepared at temperatures of 50°C and above were dissolved in benzene which is a non-solvent for acrylonitrile homopolymer, but is a good solvent for poly(methyl methacrylate) and the block copolymer. The presence of acrylonitrile and methyl methacrylate in the benzene-soluble macromolecule was demonstrated by pyrolysis gas chromatography, infra-red spectroscopy and differential thermal analysis.     

Poly(ester-ether) fibres

Ester-ether copolymers were prepared by melt condensation reaction using dimethyl terephthalate (DMT) and different quantities of ethylene glycol (EG) and poly(ethylene glycol) (PEG) (MW 400) in the initial monomer feed. Five copolymer samples were prepared by varying the contents of PEG on the basis of EG from 0.5 to 2.5 mol-%. The polymer samples were characterized by determination of melting points (mp) and intrinsic viscosities. The mp decreased from 258°C to 248°C on increasing the poly(ethylene oxide) segments in the backbone. Thermal stability of the copolymers also decreased by the introduction of PEG units in the backbone. The polymers were melt spun into fibres. With the increase of PEG in the copolymer fibres a decrease in tensile strength and initial modulus was observed while the elongation increased. The dye uptake and moisture regain of the copolyester fibres was considerably enhanced in comparison of poly(ethylene glycol terephthalate) (PET) fibres.     

Poly(squaryl amides)

The solution polycondensation of squaric acid with p-phenylenediamine in selected protic, aprotic or strongly acidic solvents furnishes linear polyamide structures possessing units with 1,2- as well as those with 1,3-orientation of the substituent links on the four-membered ring system. The relative occurrence of these two unit types as assessed by infra-red spectroscopy depends on the basicity of the medium, the extent of 1,2-orientation decreasing with increasing solvent basicity. The same type of polyamide results from a solution polycondensation of the diamine with diethyl squarate. These findings, contradicting earlier results of other workers, are in accord with more recent non-polymeric squaric acid amidation studies. A reference polyamide with maximum content of units possessing the 1,2-substituent orientation is synthesized from p-phenylenediamine and squaryl dichloride under low temperature solution polymerization conditions. Polymer inherent viscosities range from about 10 to 30ml/g, highest values being obtained under conditions of homogeneous polymerization.