海洋防污高分子材料的综合设计和研究

综述了海洋防污高分子材料与技术的发展现状.简介了海洋生物污损的形成过程,概述了杀生防污涂料、污损可脱附性涂层、阻止附着型防污技术以及其它现存的防污方法,并在此基础上提出了一种新的海洋防污高分子材料的综合设计方案,最后展示了有关海洋防污材料研究的最新成果.     

无皂种子分散聚合法制备单分散双重响应性微凝胶

以N-异丙基丙烯酰胺及2-乙烯基吡啶为主要单体, 采用无皂种子分散聚合法制备了单分散的、具有温度及pH双重响应性能的核-壳结构微凝胶, 并以扫描电镜及动态激光光散射等手段对微凝胶粒子的结构和性能进行了研究. 溶胀行为研究表明, 微凝胶粒子具有独立的互不干扰的温度及pH敏感性能, 其体积相变温度与纯聚N-异丙基丙烯酰胺(PNIPAM)凝胶基本一致, 说明局部分布的弱电离单体不会对PNIPAM凝胶的体积相变温度造成影响.     

苯硼酸类糖敏感微凝胶制备及其糖敏感性研究

制备了以葡聚糖作为交联剂的氨基苯硼酸类糖敏感微凝胶,用1H-NMR和FT-IR表征了其结构。利用微凝胶的不同条件下的粒径变化,深入研究了该类凝胶对糖浓度的刺激响应行为。结果表明,葡聚糖的引入使微凝胶在生理条件下具有更加优秀的依糖刺激响应行为。     

Fluorescence Investigations of “Smart” Microgel Systems

Fluorescence techniques, including lifetime, quenching, and time-resolved anisotropy measurements (TRAMS), were used to study microgel systems based upon N-isopropylacrylamide (NI-PAM) using pyrene as a fluorescent probe. These experiments have revealed that poly(N-isopropylacrylamide) (PNIPAM) nanoparticles undergo a phase transition at a lower critical solution temperature (LCST), of ca. 34°C, which involves collapse of the particles into compacted, hydrophobic spheres. A degree of control over the LCST has been achieved by copolymerization of NIPAM with varying amounts of dimethylacrylamide (DMAC). Incorporation of DMAC into the gel has the effect of changing the hydrophobic to hydrophilic balance and shifts the LCST to a higher temperature. Fluorescence methods indicate that the NIPAM/DMAC gels are of a more open, water-swollen nature above the LCST than that of their PNIPAM counterparts.     

ELASTOMERIC REACTIVE MICROGELS AS TOUGHENER FOR EPOXY ADHESIVES

Elastomerie reactive microgels were evaluated as toughener for epoxy adhesives. It turned out that elastomeric microgels can improve lap shear strength and peel strength greatly. The glass transition temperature of the resin matrix was not affected by the presence of dispersed mierogel particles, and thus the microgel-toughened adhesives have a good bond strength at elevated temperatures.     

Varying the Stiffness and Diffusivity of Rod-Shaped Microgels Independently through Their Molecular Building Blocks

Microgels are water-swollen, crosslinked polymers that are widely used as colloidal building blocks in scaffold materials for tissue engineering and regenerative medicine. Microgels can be controlled in their stiffness, degree of swelling, and mesh size depending on their polymer architecture, crosslink density, and fabrication method—all of which influence their function and interaction with the environment. Currently, there is a lack of understanding of how the polymer composition influences the internal structure of soft microgels and how this morphology affects specific biomedical applications. In this report, we systematically vary the architecture and molar mass of polyethylene glycol-acrylate (PEG-Ac) precursors, as well as their concentration and combination, to gain insight in the different parameters that affect the internal structure of rod-shaped microgels. We characterize the mechanical properties and diffusivity, as well as the conversion of acrylate groups during photopolymerization, in both bulk hydrogels and microgels produced from the PEG-Ac precursors. Furthermore, we investigate cell-microgel interaction, and we observe improved cell spreading on microgels with more accessible RGD peptide and with a stiffness in a range of 20 kPa to 50 kPa lead to better cell growth.     

Molecular motions in low cross-linked poly(N-isopropylacrylamide) microgels

Non-ionic N-isopropylacrylamide (PNIPAM) microgel is employed to investigate the molecular motion of polymer chains in the swollen and collapsed states. This study is performed using incoherent elastic (IES) and quasielastic neutron scattering (IQNS). IES measurements show an increase of both, the elastic intensity and the oscillations of the polymer network vibrational amplitude at the transition temperature. IQNS was measured at two different selected temperatures 290 K and 327 K corresponding to the swollen and collapsed states, respectively. The diffusion constant from IQNS experiments decreases nearly two orders of magnitude when the microgel de-swells and finally collapses.     

Evidences of a hydrolysis process in the synthesis of N-vinylcaprolactam-based microgels

The hydrolysis process suffered by vinylcaprolactam (VCL) monomer during polymerization and the way of avoiding it is a matter of considerable interest when the final material is used in biomedical applications. In this work, in order to study the hydrolysis process in the synthesis of VCL-based microgels, VCL was polymerized by emulsion polymerization in batch and semi-batch reactors by using N,N′-methylenebisacrylamide (BA) as cross-linker and potassium persulfate (KPS) as initiator. Moreover, the partial conversion evolutions of VCL and BA were analyzed by ¹H NMR. The colloidal characterization was carried out by measuring the final average diameters as a function of temperature. The results showed that there were two competitive reactions (hydrolysis and propagation) in the polymerizations carried out in the absence of a buffer. However, VCL did not suffer hydrolysis by adding a buffer in the recipes. A new reliable method for the determination of the partial conversions was developed using the quantitative NMR method. The final cross-linked colloidal particles (microgel particles) obtained in the buffered reaction presented the conventional swelling de-swelling behavior corresponding to temperature sensitive microgels.     

Effects of hectorite content on the temperature-sensitivity of PNIPAM microgels

A new method, adopting inorganic clay (synthetic hectorite) as a physical cross-linker, was used to prepare poly(N-isopropylacrylamide) (PNIPAM) microgels via surfactant-free emulsion polymerization. The effect of hectorite content on the temperature-sensitivity of PNIPAM microgels was investigated by means of DLS, UV/Vis and DSC. It was found that, in the absence of surfactant, with increasing hectorite content, the particle size tends to decrease to 300 nm at room temperature, while increases as weight ratio (WR) of hectorite and N-isopropylacrylamide (NIPAM) exceeds 21%. Furthermore, with increasing WR from 7% to 21%, the volume phase transition temperature of PNIPAM microgels has little shift, while decreases slightly when WR increases up to 28%.     

Hydrogel microparticles from lithographic processes: novel materials for fundamental and applied colloid science

In recent years there has been a surge in methods to synthesize geometrically and chemically complex microparticles. Analogous to atoms, the concept of a "periodic table" of particles has emerged and continues to be expanded upon. Complementing the natural intellectual curiosity that drives the creation of increasingly intricate particles is the pull from applications that take advantage of such high-value materials. Complex particles are now being used in fields ranging from diagnostics and catalysis to self-assembly and rheology, where material composition and microstructure are closely linked with particle function. This is especially true of polymer hydrogels, which offer an attractive and broad class of base materials for synthesis. Lithography affords the ability to engineer particle properties a priori and leads to the production of homogenous ensembles of particles. This review summarizes recent advances in synthesizing hydrogel microparticles using lithographic processes and highlight a number of emerging applications. We discuss advantages and limitations of current strategies, and conclude with an outlook on future trends in the field.