Fifteen chemistries for autonomous external self-healing polymers and composites

This review aims at guiding both new and established researchers in the field of self-healing by providing a clear overview of the fifteen most important chemistries used in autonomous external self-healing systems until today, together with their healing potential for different matrix materials and types of mechanical damage. The described self-healing systems require no manual intervention or additional stimulus for the self-healing event to take place (autonomous) and utilize added healing agents to repair the damage (external). A range of recent developments is discussed with indication of their strengths and weaknesses. An attempt is also made to demonstrate the research opportunities that are still available for each described system and to find the areas that require further elaboration. As such, this review can help to point the reader in the directions these self-healing materials could follow in the future.     

Poly(HEMA)/cyclodextrin‐based hydrogels for subconjunctival delivery of cyclosporin A

To enhance the solubility and ocular permeability of immunosuppressive agent, cyclosporine A (CsA), three types of delivery systems were prepared using (2‐hydroxypropyl)‐β‐cyclodextrin (HPβCD), and 2‐hydroxyethyl methacrylate (HEMA). Those systems are (i) hydrogels of HPβCD with crosslinking agent ethylene glycol diglycidylether, (ii) poly(HEMA) hydrogels, and (iii) different amounts of HPβCD‐containing poly(HEMA) hydrogels indicated as poly(HEMA‐co‐HPβCD). In the presence of HEMA, hydrogels have desired mechanical integrity with lower equilibrium content than that of hydrogels without HEMA. CsA was loaded into the HPβCD‐based hydrogels by embedding from its aqueous suspensions in higher amounts than that of the poly(HEMA) hydrogels that were loaded by CsA–HPβCD complex solution. Although the poly(HEMA) hydrogels are releasing total CsA in 3 days, long‐term release was realized from HPβCD‐based hydrogels. For subconjunctival administration, regarding to the amounts of loaded CsA, release profiles, and mechanical integrity, the most suitable system is poly(HEMA‐co‐HPβCD) hydrogels in high HPβCD content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40397.     

Adhesion Improvement by UV Grafting onto Polyolefin Surfaces

High Density Poly(ethylene) (HDPE) and Poly(propylene) (PP) were subjected to several surface treatments, namely UV grafting of hydroxyethylmethacrylate (HEMA), plasma deposition of HEMA and oxygen plasma treatment. Treated surfaces were subjected to two post-treatment routines (extraction with ethanol and high temperature aging). The effect of these treatments on the adhesion of HDPE and PP to epoxy coated studs was evaluated by a pull test. No adhesion at all was recorded on untreated samples. On the other hand, all the treatments yield high bond strength in the case of HDPE: an average bond strength of about 290 kg/cm² and of about 200 kg/cm² was observed after UV grafting and plasma treatments. The treated samples were practically insensitive to post-treatments. As to PP, which undergoes chain scission in plasma, it is best treated by the comparatively milder conditions of UV grafting, which yields an average bond strength similar to that observed on HDPE. O₂ and HEMA-plasma-treated PP show a mean bond strength close to 50 kg/cm², and are deeply affected by the post-treatment routines.     

Synthesis and characterizations of hydrogel based on PVA-AE and HEMA

PVA-AE, an etherification product of polyvinyl alcohol and allyl bromide, was synthesized and copolymerized with HEMA (2-hydroxyethyl methyl methacrylate) to obtain two copolymers-co-E1H9 (10% PVA-AE/90%HEMA, w/w) and co-E2H8 (20%PVA-AE/80%HEMA). The presence of PVA-AE reduced the water content from 32 % to 27 % in the resultant copolymer. The co-E2H8 copolymer had a higher tensile strain and lower elastic modulus (0.35 MPa) as compared with polyHEMA and co-E1H9 (3.9 and 2.28 MPa, respectively), The cell culture test shows that the copolymers resist cell attachment. The PVA-AE derivatives were also tested for their dentine bonding ability as an additive to HEMA. The results indicated that the dentine tensile bonding strength attained by the mixture of PVA-AE in HEMA was lower than that of the PVA-AA/HEMA dentine bonding agent that we had developed previously. The PVA-AE/HEMA copolymers have great potential for application as the basis material for anti-adhesion membranes.     

环氧氯丙烷活化甲基丙烯酸羟乙酯-苯乙烯共聚球状珠体及其在固定青霉素酰化酶中的应用

合成了甲基丙烯酸羟乙酯-苯乙烯共聚球状珠体,并对环氧氯丙烷活化该球状珠体的条件进行了研究.结果表明,在反应温度为37.5℃、NaOH浓度为1.2 mol/L、反应时间24 h的条件下,珠体的活化度可以达到2 000 μmol/g.将该珠体用作固定化酶载体的初步研究表明,固定青霉素酰化酶的活力可达360 U/g(干重).     

Adhesion Improvement by UV Grafting onto Polyolefin Surfaces

High Density Poly(ethylene) (HDPE) and Poly(propylene) (PP) were subjected to several surface treatments, namely UV grafting of hydroxyethylmethacrylate (HEMA), plasma deposition of HEMA and oxygen plasma treatment. Treated surfaces were subjected to two post-treatment routines (extraction with ethanol and high temperature aging). The effect of these treatments on the adhesion of HDPE and PP to epoxy coated studs was evaluated by a pull test. No adhesion at all was recorded on untreated samples. On the other hand, all the treatments yield high bond strength in the case of HDPE: an average bond strength of about 290 kg/cm² and of about 200 kg/cm² was observed after UV grafting and plasma treatments. The treated samples were practically insensitive to post-treatments. As to PP, which undergoes chain scission in plasma, it is best treated by the comparatively milder conditions of UV grafting, which yields an average bond strength similar to that observed on HDPE. O₂ and HEMA-plasma-treated PP show a mean bond strength close to 50 kg/cm², and are deeply affected by the post-treatment routines.     

HEMA/NVP共聚水凝胶的合成与性能

以甲基丙烯酸2-羟乙酯(HEMA)和N-乙烯基吡咯烷酮(NVP)为原料,偶氮二异丁腈为引发剂,二甲基丙烯酸乙二醇酯(EGDMA)为交联剂,采用溶液聚合法合成HEMA／NVP共聚水凝胶。对其进行了红外光谱分析,考察了交联剂用量(EGDMA)和NVP用量等对该水凝胶材料性能的影响,研究表明该水凝胶具有良好的力学性能与合适的含水量,是一种性能良好的人工角膜材料。     

Observation of Nano-Particles in Silica/poly(HEMA) Hybrid by Electron Microscopy

The sol–gel method was employed to prepare an inorganic–organic hybrid, silica/poly(HEMA). The chemical structure of this material was analyzed by means of FTIR and solid ²⁹Si-NMR. Using TEM and low voltage FESEM imaging at high magnifications (e.g., 300 KX), the hybrid was found to comprise nano-particles whose sizes fall largely over the range 20–30 nm.     

Secondary nucleation of styrenated hydroxyl-functionalized latexes

In this study, secondary nucleation in emulsion polymerization of butyl acrylate (BA), styrene (St), and 2-hydroxyethyl methacrylate (HEMA), was investigated. Different molar ratios of BA and St were used. Average particle size, particle size distribution (PSD), polymerization kinetics, glass transition temperature (T_g), and surface tension were monitored and compared. All synthetic latexes were prepared through seeded semi-batch emulsion polymerization process. Three different BA to St ratios (1:1, 1:2, 2:1) were combined with eight different HEMA contents (0, 1, 3, 5, 10, 20, 30, 40 mol%) in monomer composition, respectively. In the case of high HEMA content (10–40 mol%) it is found that secondary nucleation is mainly affected by HEMA. Secondary nucleation at low HEMA content (1–5 mol%) is dependent on the BA to St monomer ratio, and consequently a reflection of z-mer hydrophobicity.