Chemistry of multifunctional polymers based on bis-MPA and their cutting-edge applications

Polymers play an important role in the advancement of materials for use in cutting-edge applications. A direct consequence of an increased demand for more sophisticated materials has been a drive toward developing polymers that exhibit a higher level of structural control, especially in terms of the number and type of functionalities provided within the polymer framework. A family of polymers that meets such a challenge is based on the readily available AB₂ monomer 2,2-bismethylolpropionic acid (bis-MPA) building block. Due to the ease with which the monomers can be synthesized, an array of multifunctional polymers have been produced including monodisperse dendrimers and dendrons and well-defined linear polymers as well as linear-dendritic hybridizations. This review outlines the evolution of the synthetic strategies for developing novel polymeric architectures based on bis-MPA and their assessment in both solution and substrate-based innovative applications.     

Lipase‐catalyzed synthesis of aliphatic poly(β‐thioether ester) with various methylene group contents: thermal properties,crystallization and degradation

A series of novel aliphatic poly(β‐thioether ester)s with various methylene group contents were prepared by direct lipase‐catalyzed polycondensation of the monomer with an acid‐labile β‐thiopropionate group. The polycondensation reaction using immobilized lipase B from Candida antarctica was carried out in diphenyl ether at 90 °C. Poly(β‐thioether ester)s with high molecular weights of 20 500–57 000 Da and narrow polydispersities in the range 1.40–1.48 were obtained. Thermogravimetric analysis, differential scanning calorimetry and wide‐angle X‐ray diffraction were used to investigate the thermal properties and crystal structures of these polyesters. All the poly(β‐thioether ester)s were semicrystalline polymers and thermally stable up to at least 200 °C. In vitro degradation studies showed that they can rapidly degrade under acidic conditions by the hydrolysis of the β‐thiopropionate groups, suggesting their potential as acid‐degradable polymeric materials. © 2019 Society of Chemical Industry     

Fair‐Weather Friends: Evidence of Lipoxin Dysregulation in Neurodegeneration

Lipoxins (LXs) are autacoids, specialized proresolving lipid mediators (SPMs) acting locally in a paracrine or autocrine fashion. They belong to a complex superfamily of dietary small polyunsaturated fatty acid (PUFA)–metabolites, which direct potent cellular responses to resolve inflammation and restore tissue homeostasis. Together, these SPM activities have been intensely studied in systemic inflammation and acute injury or infection, but less is known about LX signaling and activities in the central nervous system. LXs are derived from arachidonic acid, an omega‐6 PUFA. In addition to well‐established roles in systemic inflammation resolution, they have increasingly become implicated in regulating neuroinflammatory and neurodegenerative processes. In particular, chronic inflammation plays a central role in Alzheimer's disease (AD) etiology, and dysregulated LX production and activities have been reported in a variety of AD rodent models and clinical tissue samples, yet with complex and sometimes conflicting results. In addition, reduced LX production following retinal injury has been reported recently by the authors, and an intriguing direct neuronal activity promoting survival and homeostasis in retinal and cortical neurons is demonstrated. Here, the authors review and clarify this growing literature and suggest new research directions to further elaborate the role of lipoxins in neurodegeneration.     

Macrophage Immunomodulation Through New Polymers that Recapitulate Functional Effects of Itaconate as a Power House of Innate Immunity

Itaconate (ITA) is an emerging powerhouse of innate immunity with therapeutic potential that is limited in its ability to be administered in a soluble form. A library of polyester materials that incorporate ITA into polymer backbones resulting in materials with inherent immunoregulatory behavior is developed. Harnessing hydrolytic degradation release from polyester backbones, ITA polymers result in the mechanism specific immunoregulatory properties on macrophage polarization in vitro. In a functional assay, the polymer-released ITA inhibits bacterial growth on acetate. Translation to an in vivo model of biomaterial associated inflammation, intraperitoneal injection of ITA polymers demonstrate a rapid resolution of inflammation in comparison to a control polymer silicone, demonstrating the value of sustained biomimetic presentation of ITA.     

涤纶工业丝环吹风改造的设计计算

应用PET纤维的冷却成形理论 ,结合空气调节的相关知识 ,提出了环吹风的设计计算方法 ,对涤纶工业丝环吹风进行了设计改造 ,满足了纺丝工艺要求     

非饱和土的抗剪强度理论研究

从孔隙水的存在状态出发 ,围绕Bishop抗剪强度公式中存在的几个疑点展开讨论 .认为非饱和土中支配强度和变形的应力之所以不同 ,是因为非饱和土中存在一种性质与有效应力不同的应力———内部应力 ,它不传递 ,仅影响土的塑性变形 .同时还对Bishop ,Fredlund和卢肇钧提出的抗剪强度公式中的参数测试方法进行分析 ,指出 :各种抗剪强度理论在概念上都是相同的 ,其区别仅在于确定由吸力产生的那部分有效应力时采用的参数和测试方法不同     

探讨缩聚催化剂对聚酯切片质量的影响

通过试验，分析比较了江西Sb2O3、南宁Sb2O3和大连Sb(Ac)3三种缩聚催化剂对聚酯切片质量的影响。试验结果表明，Sb(Ac)3是优良的缩聚催化剂。     

Development of co-continuous structure in liquid crystalline polyester

We investigated liquid crystallization of liquid crystalline polyester BB-5 during isothermal annealing by digital high-fidelity microscope and light scattering. A liquid crystalline spherical domain having a radius of micrometers appeared by annealing at around 180 °C. The domain grew dendritically in all directions. Neighboring liquid crystalline regions coalesced and then interconnected. The interconnected structure changed to a co-continuous two-phase structure with increasing ordering of the liquid crystalline phase, and the interface between the liquid crystalline phase and the isotropic phase became smoother over time. Liquid crystallization stopped before volume filling the whole space, and the liquid crystalline phase and isotropic phase coexisted. The liquid crystalline region became narrower with an increase in the temperature of the liquid crystallization. Such structural development is different from the liquid-liquid phase separation via spinodal decomposition, and it may be attributed to the segregation of non-liquid crystallizable low molecular weight molecules from the growth front by fractionation of the molecular weight distribution during the liquid crystallization in terms of the instability of the diffusion-controlled interface.     

饱和—非饱和土体非稳定渗流数值分析

本文对一般的非饱和渗流有限元计算方法加以改进，有效地消除了非饱和渗流数值计算中存在的数值弥散现象。同时还提出了一种简便有效的逸出面处理新方法，并给出了非饱和非稳定渗流计算的实例。     

磷－溴双元素阻燃涤纶切片的研制

分析了磷－溴（Ｐ－Ｂｒ）阻燃剂的特性及阻燃机理。应用Ｐ－Ｂｒ阻燃剂进行了阻燃涤纶切片的开发研制试验，结果表明：Ｐ－Ｂｒ阻燃剂阻燃效果好、能高度分散并有良好的热稳定性，其所制阻燃涤纶切片有良好的可纺性。