CE detection of N‐(3‐dimethylaminopropyl)‐N‐carbodiimide/N‐hydroxysuccinimide‐coupled proteins after homo‐ and hetero‐crosslinking reactions

Protein–protein conjugates formed by carbodiimide crosslinking reactions have been analyzed for the first time using CE. Lysozyme and BSA were chosen as model proteins to study the efficacy of N‐(3‐dimethylaminopropyl)‐N‐ethylcarbodiimide and N‐hydroxysuccinimide as crosslinkers. Detection of the molecular mass increase was checked by SDS‐PAGE. Commercially available, PVA‐coated capillaries showed appropriate selection, while phospho‐deactivated and dynamic PVA‐coated capillaries did not give suitable resolution. CE was found to be an efficient tool to characterize homo‐ (lysozyme–lysozyme) and hetero‐ (lysozyme–BSA) protein coupling by suitable variations of electrophoretic mobilities.     

热稳定剂对PVC紫外光老化过程中微观结构及宏观性能演变的影响

通过UV-Vis、FTIR、DSC、以及色差、力学性能的测试表征,实时追踪分析了在紫外光老化过程中,含Pb、Sn以及Ca-Zn热稳定剂的PVC体系微观结构和宏观性能的演变过程.结果表明,在相同光老化条件下,PVC/Pb、PVC/Sn和PVC/Ca-Zn体系的微观结构变化规律基本一致,过程中主要的化学反应是,大分子吸收光能后,发生脱HCl生成共轭双键的反应、生成羰基的氧化反应、交联反应和降解反应;不同热稳定剂的作用,主要表现在对于微观结构变化的幅度和动力学过程的影响不同.相应地,3种体系的外观色差和力学性能的变化规律也相似,但色差的变化程度和速度以及老化后力学性能的保持率因所含热稳定剂的不同而不同,其中含Sn体系的颜色稳定性最好,含Pb体系的力学性能保持率最高。     

The sensitizing effect of acrylates on radiation vulcanization of natural rubber latex

The sensitizing effect of acrylates on radiation vulcanization of natural rubber latex was studied. The results indicate that Gc value of crosslinking (Gc) will be higher at the same radiation dose when a sensitizer exists, and Gc value decreases with the increase of radiation dose (D) conforming to the formula Gc=KD^-α, where K and α are constants depending on sensitizers. The more sensitizers added, the greater the Gc value. However, the viscosity of the natural rubber latex also increases rapidly along with the increase of sensitizers added.Some sensitizers, such as TMPTA, can decrease the optimum dose from about 200 kGy to approximately 20 kGy according to our experiment. The tensile strength of the film can reach round 20 MPa. Other physical properties are comparable to those of unsensitized.     

In situ-preparation and characterization of silver-HEMA/PEGDA hydrogel matrix nanocomposites: Silver inclusion studies into hydrogel matrix

Poly(ethylene glycol) diacrylate (PEGDA) of different molecular weights (Mn = 575 and 700) was used as crosslinking agent for the photopolymerization of 2-hydroxyethyl methacrylate (HEMA) in order to obtain HEMA/PEGDA-based hydrogels. Composites were synthesized in situ employing a new methodology that implies the addition of different quantities of silver nitrate aqueous solution to the monomer mixture with the finality to obtain hydrogels with different silver nanoparticles’ spatial density and distribution. Samples were characterized by thermal, optical, spectroscopic and structural/morphological methods. Thermal studies showed that the increase of PEGDA molecular weight and the AgNO₃ concentration in the reaction mixture enhance the glass transition temperature and the thermal stability of the composites. This behavior could be related to the silver coordination with the polymer network. Infrared spectroscopy with Fourier transform and Raman analyses were realized in order to corroborate the sample chemical structure by the identification of specific functional groups. Surface hydrogel morphology was visualized with scanning electron microscopy analysis, detecting a homogeneous micro-porous surface for the samples obtained from high molecular weight PEGDA. Presence of silver nanoparticles was established by X-ray fluorescence spectroscopy and UV/Vis methods. In this last case, the characteristic silver nanoparticle plasmon was observed. Using Transmission Electron Microscopy it was possible to visualize a homogeneous spatial distribution of spherical silver nanoparticles with very narrow diameter distribution that rounds about 14–21 ± 5 nm. In general, the silver nanoparticle presence in the compounds enhances considerably their thermal/morphological characteristics.     

硬链段浓度对RIM交联聚氨酯结构和性能的影响

用l-MDI/1,4-BDO/PPO-EO快反应体系,考察硬段浓度对聚氨酯结构与性能的影响。发现样品的交联度、模量和抗张强度随硬段浓度增加而提高,交联趋向均匀,断裂伸长率在浓度30％处出现最大值。ATR-FTIR和DSC分析表明,微相分离程度随硬段浓度增大而降低。     

低浓度HPAM/AlCit交联体系的27Al NMR研究

用27Al NMR谱研究了高分子量低浓度的部分水解聚丙烯酰胺(HPAM)与柠檬酸铝(AlCit)体系交联反应过程中Al的化学位移和Al的自旋-晶格弛豫时间的变化. 结果表明, HPAM与AlCit反应后, 与HPAM分子链上的羧基发生配位交联的Al的化学位移向低场移动, 而不参与交联反应的AlCit分子结构中Al的化学位移基本不变. HPAM/AlCit交联体系中存在三种形态的Al, 分别对应三种不同的自旋-晶格弛豫时间. 当HPAM的质量浓度≤200 mg/L时, HPAM与AlCit反应过程中交联态Al的自旋-晶格弛豫时间τ13随反应进行变小, HPAM与AlCit主要发生分子内交联反应. 当HPAM的质量浓度≥250 mg/L时, HPAM与AlCit反应过程中交联态Al的自旋-晶格弛豫时间τ13随反应进行变大, HPAM与AlCit主要发生分子间交联反应.     

Deuterium NMR Studies on the Orientational Order Generated in Strained Rubbers

The present paper deals with the induced orientational order of the probe molecules dissolved in the uniaxially strained rubbers measured by using deuterium NMR. The distinctive dependence of the quadrupolar splitting on the swelling, elongation and crosslinking density was observed. The orientational order arising from the correlation between chain segments decreases with the increase of the numbers of both links between junctions and solvent molecules around segments.     

聚合物结构对包膜缓释肥缓释性能的影响

研发和使用缓控释肥能有效解决普通肥料利用率低以及由于化肥使用过量而引起的环境问题。聚合物包膜型缓控释肥是缓控释肥中的一种,影响其缓释性能的因素如环境因素、包膜厚度、加工工艺等,前人已研究较多。聚合物结构对于缓释性能的影响也很重要,而这方面研究较少。本文主要讨论了聚合物结晶性、分子亲疏水性、分子链柔顺性、交联等结构因素对缓释性能的影响。深入研究聚合物结构对缓释性能的影响有助于缓控释材料的创新;能为聚合物包膜材料的设计、聚合物缓控释肥的研发及生产提供一定的理论依据。     

Time-intensity transformation and internal stress in UV-curable hyperbranched acrylates

The photocuring of three different highly functional acrylates—Di-pentaerythritol penta/hexaacrylate (DPHA) and two hyperbranched molecules (HBP), one with a stiff polyester and one with a more flexible polyether structure—was investigated by means of photorheology, photo differential scanning calorimetry, and beam bending. Special attention was paid to the influence of the composition of DPHA/HBP reactive blends and UV intensity on gelation and vitrification and the resulting dynamics of the internal stress. It was found that adding HBPs to DPHA did not influence gelation significantly, but shifted the onset of vitrification to higher conversions and thus caused lower internal stresses in the material. Increasing UV intensity increased both the conversion at vitrification, thus retarding the build-up of internal stresses, and the ultimate conversion, thus increasing the final stress level. The obtained conversion, gelation, and vitrification data were assembled into time-intensity transformation diagrams, thus providing a useful tool for optimizing photocuring. This paper was presented at Annual European Rheology Conference (AERC) held in Hersonisos, Crete, Greece, April 27–29, 2006.     

Preparation of sulphonate-containing polymer particles <Emphasis Type="Italic">via</Emphasis> semi-continuous emulsion copolymerizaion of styrene and sodium styrene sulphonate

Submicron-sized P(St-NaSS) latexes were prepared via a semi-continuous emulsion copolymerization of styrene (St) and sodium styrene sulphonate(NaSS) in the presence of anionic surfactant,in which NaSS aqueous solution and St were separately dropwise charged into the polymerization system at the same time.The hydrodynamic diameter of the latex particles was measured by dynamic light scattering(DSL) method,and the NaSS unit content of the purified copolymer by water extraction was calculated based on the elementary analysis.Results showed that the copolymerization could be performed smoothly with the monomer conversion more than 96%in the absence of crosslinker,and PNaSS homopolymer could be removed from the latex product by water extraction for 28 h.The weight loss in the water extraction tended to decrease and the NaSS unit content of the purified copolymer tended to increase with the increase of monomer feeding time, and both of them increased with the increase of NaSS/St mole ratio in the charge.The introduction of divinyl benzene (DVB) could decrease the weight loss in the water extraction and increase the NaSS unit content of the purified copolymer. When 25/75 mole ratio of NaSS/St and 11 mol%DVB of total NaSS and St were used in the recipe,and the monomer feeding time was 3 h in copolymerization,the NaSS unit content of the purified copolymer reached 7.31 mol%.