Viscoelasticity and tack of poly(vinyl pyrrolidone)–poly(ethylene glycol) blends

The adhesive properties of blends of high molecular weight poly(vinyl pyrrolidone) (PVP) and low molecular weight poly(ethylene glycol) (PEG) were systematically investigated with a probe test and correlated with their viscoelastic properties. The material parameters that were varied were the PEG content (31–41 wt %) and the hydration rate. The 36% PEG showed the best balance of properties for a pressure‐sensitive adhesive. At low debonding rates, the debonding took place through the formation of a fibrillar structure, whereas at high debonding rates, the debonding was brittle. This transition was attributed to the breakage and reformation of hydrogen bonds between PVP units and OH groups on PEG during the large strain of the polymer chains in elongation. This transition was observed, albeit shifted in frequency, for all three compositions, and the characteristic relaxation times of the hydrogen‐bonded network were estimated. A comparison between the tack properties of the adhesives and their linear viscoelastic properties showed a very strong decoupling between the small‐strain and large‐strain properties of the adhesive, which was indicative of a pronounced deviation from rubber elasticity in the behavior of the blends. This deviation, also seen during tensile tests, was attributed to the peculiar phase behavior of the blends. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2395–2409, 2002     

聚合物表面的环境响应性

文中讨论了聚合物环境响应的多样性，此响应性可借表面改性和形成多组分聚合物以结构参数而有效地控制。响应性与生物医学材料的血液相容性及既适合极性又可用于非极性基材的粘合剂的智能特性相关。     

对黏连性肠梗阻患者术后实施综合护理干预后的护理质量评价

目的探讨对黏连性肠梗阻患者术后实施综合护理干预后的护理质量。方法选取2014年1月至2014年12月期间在湖北省团风县人民医院接受治疗的腹部手术患者100例,将患者随机分为观察组与对照组,每组患者50例。其中对照组实施常规护理,观察组实施综合护理干预,比较两组患者的临床护理效果。结果观察组患者黏连性肠梗阻发生率低于对照组,胃肠道功能的恢复时间均短于对照组,组间比较差异具有统计学意义(P0.05)。结论腹部手术患者术后实施综合护理干预可减轻对胃肠道功能的影响,降低黏连性肠梗阻的发生几率。     

Nanomechanics of Poly(catecholamine) Coatings in Aqueous Solutions

Mussel‐inspired self‐polymerized catecholamine coatings have been widely utilized as a versatile coating strategy that can be applied to a variety of substrates. For the first time, nanomechanical measurements and an evaluation of the contribution of primary amine groups to poly(catecholamine) coatings have been conducted using a surface‐forces apparatus. The adhesive strength between the poly(catecholamine) layers is 30‐times higher than that of a poly(catechol) coating. The origin of the strong attraction between the poly(catecholamine) layers is probably due to surface salt displacement by the primary amine, π–π stacking (the quadrupole–quadrupole interaction of indolic crosslinks), and cation–π interactions (the monopole–quadrupole interaction between positively charged amine groups and the indolic crosslinks). The contribution of the primary amine group to the catecholamine coating is vital for the design and development of mussel‐inspired catechol‐based coating materials.     

Development of Non‐Cell Adhesive Vascular Grafts Using Supramolecular Building Blocks

Cell‐free approaches to in situ tissue engineering require materials that are mechanically stable and are able to control cell‐adhesive behavior upon implantation. Here, the development of mechanically stable grafts with non‐cell adhesive properties via a mix‐and‐match approach using ureido‐pyrimidinone (UPy)‐modified supramolecular polymers is reported. Cell adhesion is prevented in vitro through mixing of end‐functionalized or chain‐extended UPy‐polycaprolactone (UPy‐PCL or CE‐UPy‐PCL, respectively) with end‐functionalized UPy‐poly(ethylene glycol) (UPy‐PEG) at a ratio of 90:10. Further characterization reveals intimate mixing behavior of UPy‐PCL with UPy‐PEG, but poor mechanical properties, whereas CE‐UPy‐PCL scaffolds are mechanically stable. As a proof‐of‐concept for the use of non‐cell adhesive supramolecular materials in vivo, electrospun vascular scaffolds are applied in an aortic interposition rat model, showing reduced cell infiltration in the presence of only 10% of UPy‐PEG. Together, these results provide the first steps toward advanced supramolecular biomaterials for in situ vascular tissue engineering with control over selective cell capturing.

     

Application of the Scanning Kelvin Probe for the study of the corrosion resistance of interfacial thin organosilane films at adhesive/metal interfaces

The Scanning Kelvin Probe is introduced as a real time non-destructive in situ technique for the detection of de-adhesion at adhesive/metal oxide interfaces. Iron substrates and an epoxy adhesive served as model systems. Iron surfaces were coated with ultra-thin organosilane plasma polymer films from a microwave discharge and 3-(trimethoxysilyl)-propylamine films from dilute water based solutions. Surface and film characterisation was done by means of atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and infrared reflection absorption spectroscopy (IRRAS). The effect of these interfacial films on the stability of the adhesive/metal joint was studied in corrosive environments. The Scanning Kelvin Probe allows the measurement of electrode potentials at buried polymer/metal interfaces with a spatial resolution of about 100 m. The electrode potential characterises the reactivity of the interface. Moreover, by the variation of the oxygen partial pressure in the measurement chamber, local anodes and cathodes underneath the polymer can be distinguished. The kinetics of electrochemical de-adhesion can be effectively slowed down by thin 3-(trimethoxysilyl)-propylamine films at the interface. The effect of the adhesion promoter can be further improved when a thin SiO_x layer, which inhibits electron transfer reactions, and is deposited on the iron surface prior to coating with the adhesion promoter.This paper is dedicated to Mike Owen on occasion of his winning the DeBruyn medal, the first silicon chemist to do so.     

聚氨酯胶粘剂的热分解动力学研究

采用热分析技术考察了通用型聚氨酯胶粘剂在空气中的热解过程, 并通过TG方法和动力学方法研究了各步反应的活化能E、指前因子A等动力学参数. 通过等失重转化率法校验了两种方法所获得的E和A值. 结果表明, 聚氨酯胶粘剂有三个主要降解阶段, 第一降解阶段的活化能为144.31-148.35 kJ·mol^-1, 第二个降解阶段的活化能为196.96-204.26 kJ·mol^-1, 第三个降解阶段的活化能为202.97-205.27 kJ·mol^-1; 热降解过程为一级反应, 随着失重百分率的增大, 热分解反应活化能增大. 此外, 聚氨酯胶粘剂具有较高的热稳定性, 预测其在35 ℃的空气中失重5%时的热老化寿命为10年.     

Synthesis of unsaturated 7,8- and 7,9-di(hydroxymethyl)decahydro-7,8- and-7,9-dicarba-nido-undecaborate(1−) diethers

Dicarba-nido-undecaborate(1–) anions were obtained by treatment of 1,2-di(hydroxymethyl)-1,2-dicarba-closo-dodecaborane(12) diallyl ether, 1,2-di(hydroxymethyl)-1,2-dicarba-closo-dodecaborane (12), and 1,7-di(hydroxymethyl)-1,7-dicarba-closo-dodecaborane(12) with ethanolic solutions of KOH and subsequent reaction of the products with cesium and tetramethylammonium chlorides.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1821–1823, September, 1995.     

Asymptotic behavior of correlation functions for electric potential and field fluctuations in a classical one- component plasma

The correlations of the electric potential fluctuations in a classical one-component plasma are studied for large distances between the observation points. The two-point correlation function for these fluctuations is known to decay slowly for large distances, even if exponential clustering holds for the charge correlation functions. In this paper the asymptotic behavior of the generalk-point electric potential correlation functions is analyzed. Each of these correlation functions can be split into a reducible part, which is given by a sum of products of lower-order correlation functions, and a remaining irreducible part. It is shown, on the basis of an exponential clustering hypothesis for the charge correlation functions, that for allk3 the irreducible parts of the electric potential correlation functions decay faster than any inverse power of the distance, if one or more of the observation points move far away from the others. Hence, the two-point electric potential correlation function is the only one with a slow algebraic decay. The same statement holds for the correlation functions of the electric field fluctuations.