Self‐adhesive epoxy modified silicone materials for light emitting diode encapsulation

In this paper, we prepared the light emitting diode (LED) encapsulant with self‐adhesion and high refractive index. In order to improve adhesion properties, we synthesized a series of multifunctional polysiloxanes with different contents of epoxy groups via the sol–gel condensation of methylvinyldimethoxysilane, diphenylsilanediol and 3‐glycidoxypropyldimethoxymethylsilane. The structures of epoxyphenylvinyl silicone (EPVS) resins were confirmed by proton nuclear magnetic resonance and Fourier‐transform infrared. The effect of epoxy group content on the adhesion property of EPVS resins was fully studied. The performances of the LED encapsulation materials based on EPVS resins were investigated in detail. These self‐adhesive encapsulating materials showed excellent thermal stability, a high refractive index of 1.55 and good adhesive property. These EPVSs can be used as an adhesion promoter for LED encapsulation materials. Copyright © 2017 John Wiley & Sons, Ltd.     

利用一氧化碳合成高分子材料

介绍一氧化碳分别与烯烃、甲醛、胺类等化俣物共聚制备聚酮、聚酯、聚胺等，与一氧化碳被氢气还原制备聚合甲烯的化学反应原理和应用实例，以及开发利用一氧化碳合成高分子材料的动向和发展前景。     

Hydrogen-induced softening in nanocrystalline Ni investigated by nanoindentation

The influence of hydrogen on the plastic deformation of nanocrystalline nickel was analysed by recourse to nanoindentation on the uncharged and hydrogen-charged samples. It was revealed that, in nanocrystalline Ni, hydrogen significantly decreases hardness but does not alter the strain rate sensitivity. Through thermal desorption spectroscopy measurement, charged hydrogen was expected to reside in face-centred cubic lattice, grain boundaries (GBs) and vacancies rather than dislocations. The hydrogen-induced softening behaviour is discussed in terms of the possible roles of hydrogen in GB-assisted dislocation flow mechanism.     

基团贡献法研究甲基丙烯酸酯聚合物特性参数

基团贡献，Ｍａｒｋ－Ｈｏｕｗｉｎｋ方程，甲基丙烯酸２，２，３，３－四氟丙酯，甲基丙烯酸酰基氧乙酯，甲基丙烯酸乙酯，自由基聚合。     

Biodegradable Multiblock Copolymers Based on Oligodepsipeptides with Shape‐Memory Properties

Thermoplastic phase‐segregated multiblock copolymers with polydepsipeptides and PCL segments were prepared via coupling of diol and PCL‐diol using an aliphatic diisocyanate. The obtained multiblock copolymers showed good elastic properties and a shape memory. Almost complete fixation of the mechanical deformation, resulting in quantitative recovery of the permanent shape with a switching temperature around body temperature, was observed. In hydrolytic degradation experiments, a quick decrease of the molecular weight without induction period was observed, and the material changed from elastic to brittle in 21 d. These materials promise a high potential for biomedical applications such as smart implants or medical devices.

     

CAGW and TAT‐NLS peptides functionalized multitargeting gene delivery system with high transfection efficiency

Gene therapy has attracted much attention in vascular tissue engineering. However, it is still challenging to develop a novel gene carrier with multifunction to overcome the barriers in gene delivery. Herein, the multitargeting gene complexes were developed based on methoxy‐poly(ethylene glycol)‐b‐poly‐(D,L‐lactide‐co‐glycolide) (mPEG‐b‐PLGA), poly(d ,l ‐lactide‐co‐glycolide)‐g‐polyethylenimine‐g‐CAGW (PLGA‐g‐PEI‐g‐CAGW), cell‐penetrating peptide YGRKKRRQRRR (TAT), nuclear localization signals (NLS), and pEGFP‐ZNF580 (pDNA) with the purpose of enhancing the transfection of endothelial cells (ECs). The low cytotoxic multitargeting gene complexes could be easily prepared by adjusting the weight ratio of mPEG‐b‐PLGA and PLGA‐g‐PEI‐g‐CAGW. Meanwhile, CAGW peptide with selectively ECs‐targeting ability and TAT‐NLS peptide sequence with both cell‐penetrating ability and nuclear targeting capacity were simultaneously introduced into gene complexes in order to enable them with the multitargeting function so as to improve their gene delivery capacity. The pDNA loading capacity of these gene complexes was confirmed by agarose gel electrophoresis assay. MTT results demonstrated that the relatively cell viability of the multitargeting gene complexes was higher than those of other groups. These multitargeting gene complexes showed higher internalization and transfection efficiencies than other groups. These results revealed that CAGW and TAT‐NLS peptide sequences benefited for efficient gene delivery. Furthermore, the wound healing assay demonstrated that the multitargeting gene complexes could promote the proliferation and migration of ECs. These results collectively demonstrated that CAGW and TAT‐NLS peptides functionalized gene delivery system could effectively enhance the transfection of ECs, which has great potential in vascular tissue engineering.     

An Electrochemical Study of the Surface Hybridization Process of Morpholino‐DNA: Thermodynamics and Kinetics

Morpholino (MO) is a neutral analogue of DNA, which shows promise in the development of DNA biosensors and diagnostic devices. The present study explores the hybridization process of a surface‐attached MO 22‐mer with 10‐mer and 20‐mer DNA targets on a gold electrode. The melting process of the MO‐DNA duplex at the electrode/buffer interface is recorded using cyclic voltammetry. These results show that the length of target DNA, the binding location of the target DNA on the surface‐immobilized MO chain, and electrostatic forces from neighbouring duplexes all modulate the stability and hybridization kinetics of the DNA targets with the MO probes. Melting temperatures for immobilized MO‐DNA duplexes are found to be insensitive to ionic strength, provided the duplexes do not have a linker. Although the melting temperature does not shift appreciably with ionic strength, the maximum hybridization yield does. This somewhat surprising observation is considered to originate from an electrostatic limit on the extent of attainable hybridization. It is also reported that hybridization tends to initiate at the upper half of MO probes.     

Lipase catalyzed copolymerization of 3(S)-isopropylmorpholine-2,5-dione and D,L-lactide

The polymerization and copolymerization of 3(S)-isopropylmorpholine-2,5-dione (IPMD) and D,L-lactide (DLLA) were carried out in the presence of Porcine pancreatic lipase type II (PPL) as a catalyst at 100 degrees C for 168 h. Homopolymers and random copolymers of various compositions were obtained with a carboxylic acid group at one end and a hydroxyl group at the other end. The glass transition temperature of the copolymers decreases with increasing mole fraction of DLLA residue in the copolymers.     

Lipase‐Catalyzed Ring‐Opening Polymerization of 3(S)‐sec‐Butylmorpholine‐2,5‐dione

Lipase‐catalyzed ring‐opening bulk polymerizations of 3(S)‐sec‐butylmorpholine‐2,5‐dione (BMD) were investigated. Selected commercial lipases were screened as catalysts for BMD polymerization at 110°C. Polymerizations catalyzed with 10 wt.‐% of lipase PPL and PC result in BMD conversions of about 70% and in molecular weights of the products ranging from 5 500 to 10 700. Lipases MJ, CR and ES showed lower catalytic activities for the polymerization of BMD. Poly(3‐sec‐butylmorpholine‐2,5‐dione) has a carboxylic acid group at one end and a hydroxy group at the other end. During the polymerization racemization of the isoleucine residue takes place. Lipase PPL was selected for a more detailed study. The apparent rate of polymerization increases with increasing PPL concentration when the polymerization temperature is 110°C. When the PPL concentration is 5 and 10 wt.‐% with respect to the monomer, a conversion of about 70% is reached after 5 d and 3 d, respectively, while for a PPL concentration of 1 wt.‐% the conversion is less than 7% even after 6  d. High concentrations of PPL (10 wt.‐%) result in high M_n values (< 4  d). The highest molecular weight poly(BMD), M_n = 19 900, resulted from a polymerization conducted at 120°C with 5 wt.‐% PPL for 6 d. The general trend observed by varying the polymerization temperature is as follows: (i) monomer conversion and M_n increase with increasing reaction temperature from 110 to 125°C, (ii) monomer conversion and M_n decrease with an increase in reaction temperature from 125 to 130°C. Water content was found to be an important factor that controls both the conversion and the molecular weight. With increasing water content, enhanced polymerization rates are achieved while the molecular weight of poly(BMD) decreases.     

Enzyme‐catalyzed ring‐opening polymerization of 3(S)‐isopropylmorpholine‐2,5‐dione

The enzymatic ring‐opening polymerization of a 6‐membered cyclic depsipeptide, 3(S)‐isopropylmorpholine‐2,5‐dione in the bulk, was investigated by using lipases as catalysts at 100 and 130°C. Unchanged monomer was recovered in the absence of the enzyme or using an inactivated enzyme, indicating that the present polymerization proceeds through enzymatic catalysis. Poly(3‐isopropylmorpholine‐2,5‐dione) has a carboxylic acid group at one end and a hydroxy group at the other end.