Atom transfer radical polymerization (ATRP): A versatile and forceful tool for functional membranes

The progress in atom transfer radical polymerization (ATRP) provides an effective means for the design and preparation of functional membranes. Polymeric membranes with different macromolecular architectures applied in fuel cells, including block and graft copolymers are conveniently prepared via ATRP. Moreover, ATRP has also been widely used to introduce functionality onto the membrane surface to enhance its use in specific applications, such as antifouling, stimuli-responsive, adsorption function and pervaporation. In this review, the recent design and synthesis of advanced functional membranes via the ATRP technique are discussed in detail and their especial advantages are highlighted by selected examples extract the principles for preparation or modification of membranes using the ATRP methodology.     

Polymer brush coatings for combating marine biofouling

A variety of functional polymer brushes and coatings have been developed for combating marine biofouling and biocorrosion with much less environmental impact than traditional biocides. This review summarizes recent developments in marine antifouling polymer brushes and coatings that are tethered to material surfaces and do not actively release biocides. Polymer brush coatings have been designed to inhibit molecular fouling, microfouling and macrofouling through incorporation or inclusion of multiple functionalities. Hydrophilic polymers, such as poly(ethylene glycol), hydrogels, zwitterionic polymers and polysaccharides, resist attachment of marine organisms effectively due to extensive hydration. Fouling release polymer coatings, based on fluoropolymers and poly(dimethylsiloxane) elastomers, minimize adhesion between marine organisms and material surfaces, leading to easy removal of biofoulants. Polycationic coatings are effective in reducing marine biofouling partly because of their good bactericidal properties. Recent advances in controlled radical polymerization and click chemistry have also allowed better molecular design and engineering of multifunctional brush coatings for improved antifouling efficacies.     

基于DMAEMA的可聚合离子液体及其与HEMA交联共聚物凝胶的研究

以丙酮为溶剂,分别采用丙酸(AS)、磷酸(H3PO4)以及2-丙烯酰胺基-2-甲基丙磺酸(AMPS)中和甲基丙烯酸-N,N-二甲基胺基乙酯(DMAEMA),然后减压蒸馏去除溶剂,合成了3种可聚合离子液体DMAEMA-AS/H3PO4/AMPS,采用差示扫描量热(DSC)表征其玻璃化温度(Tg)。以过硫酸铵(APS)为引发剂,以N,N-亚甲基双丙烯酰胺(MBAM)为交联剂,甲基丙烯酸-2-羟基乙酯(HEMA)分别与3种可聚合离子液体在水溶液中交联共聚,合成了Poly(HEMA-co-DMAEMA-AS/H3PO4/AMPS)凝胶,采用重量法研究了3种凝胶的溶胀行为。结果表明,DMAEMA-AS/H3PO4/AMPS的玻璃化温度分别为-61.9℃、76.2℃、-45.8℃,Poly(HEMA-co-DMAEMA-AS)和Poly(HEMA-co-DMAEMA-H3PO4)凝胶可在水及多种有机溶剂中溶胀,而Poly(HEMA-co-DMAEMA-AMPS)凝胶在任何溶剂中均不溶胀,并初步探讨了产生这种现象的原因。     

Aspects of enamel bonding using experimental silanes for orthodontic adhesion

This in vitro study investigates bonding to enamel using experimental silane-based primers with and without 2-hydroxyethylmethacrylate (HEMA) under various artificial ageing methods. One hundred and fifty sound extracted human premolars were used and randomly assigned to three experimental study groups. They were first acid-etched for 15 s, rinsed with water spray, air dried, and applied 0.3 ml of artificial saliva on the enamel surfaces. Two groups of enamel surfaces were primed using silane-based experimental primers (1.0 vol% of 3-isocyanatopropyltrimethoxysilane and 0.5 vol% of bis-1,2-(triethoxysilylethane) with and without 25% HEMA) while one group was served as control. Then, stainless steel premolar orthodontic brackets were fixed onto teeth with orthodontic resin composite. The specimens from each group (n=10) were stored under different ageing conditions: thermo-cycling (500, 2000, and 6000 cycles), storage in artificial saliva for 24 h, and for one year. The shear adhesion (bond) strength (SBS) was tested by using a universal testing machine at a crosshead speed of 1.0 mm/min. Surface morphology and failure modes at the debonded interfaces were examined using SEM. Two-way ANOVA and post hoc tests were used to compare the SBS (α=0.05). The results suggested that an experimental primer with 25% HEMA, after 24 h storage in artificial saliva, produced the highest mean SBS (22.1 MPa, SD 2.2 MPa). The lowest mean value (5.8 MPa, SD 1.1 MPa) was obtained with the control group thermo-cycled (6000 cycles). There was a significant difference between the experimental primers (p<0.001) and artificial ageing (p<0.001). We conclude that 25% HEMA inclusion in silane primer could provide satisfactory adhesion strength, and 500 cycles of thermo-cycling (ISO TR 11450) does not correlate with 1-year artificial saliva storage for enamel bonding test.     

Mechanical and tribological properties of poly(hydroxyethyl methacrylate) hydrogels as articular cartilage substitutes

Poly(hydroxyethyl methacrylate) (p(HEMA)) hydrogels have been proposed as promising biomaterials to replace damaged articular cartilage. A major obstacle to their use as replacement bearing tissue is their poor mechanical properties in comparison with healthy articular cartilage. The purpose of this study was to obtain p(HEMA) hydrogels with physicochemical and mechanical properties close to healthy articular cartilage, by introducing a hydrophilic monomer, namely acrylic acid (AA). Formulations of hydrogels with different amounts of hydrophilic monomer (acrylic acid, AA) were synthesized and tested: p(HEMA), p(HEMA-co-5%AA), p(HEMA-co-25%AA). The macro-mechanical tests were reproduced at nanoscale in order to verify if the superficial properties of the hydrogels are similar to the bulk ones.     

Tuning the thermoresponsive properties of poly(oligo(propylene glycol) methacrylate) hydrogels via gradient copolymerization with 2-hydroxyethyl methacrylate

Gamma radiation was used to prepare copolymer hydrogel libraries based on oligo(propylene glycol) methacrylate (OPGMA) and 2-hydroxyethyl methacrylate (HEMA); a complete screening in composition of P(OPGMA/HEMA) copolymers was elaborated from 0% to 100% of OPGMA. Determination of gel fraction was performed as the first step after radiation induced synthesis. Tuning of the volume phase transition temperature (VPTT) of P(OPGMA/HEMA) copolymeric hydrogels was investigated by swelling study. Additional characterization of structure and properties was conducted by FTIR, DSC, and UV-Vis spectroscopy. All results indicate that new P(OPGMA/HEMA) copolymeric hydrogels have wide diversity in thermoresponsive properties which strongly depend on their composition.     

Orthogonal ligation to spherical polymeric microparticles: Modular approaches for surface tailoring

Modular ligation strategies for the functionalization of polymeric microspheres provide new perspectives for their applications in material science. In the current trend article we highlight variable synthetic procedures for generating functional microspheres via orthogonal modular conjugation chemistries. An overview of the different surface chemistries available is provided, followed by surface-sensitive characterization techniques relevant for the microparticles. Finally, we explore future trends in modular orthogonal modification approaches on microparticles and provide an outlook on the perspectives that the field of surface-modification of polymeric microparticles holds.     

松香丙烯酸加成物与HEMA酯化及溴化反应研究

为了提高松香的附加值,利用松香和丙烯酸的Diels-Alder反应得到加成物(RA),RA进一步与甲基丙烯酸-β-羟乙酯(HEMA)反应得到酯化物(RAH),RAH再与液溴反应得到溴化物(BRAH)。以酸值为衡量指标优选出酯化反应的最佳工艺条件,并采用红外光谱(FT-IR)法和热失重分析(TGA)法对产物结构进行了表征。结果表明:酯化反应的最佳工艺条件为n(RA)∶n(HEMA)=1∶2.0,反应温度230℃,反应时间4 h,催化剂是ZnO,w(ZnO)=2%(相对于RA质量而言);RAH的热稳定性优于RA,BRAH具有一定的阻燃性能。     

Synthesis and surface properties of polydimethylsiloxane‐based block copolymers: poly[dimethylsiloxane‐block‐ (ethyl methacrylate)] and poly[dimethylsiloxane‐block‐(hydroxyethyl methacrylate)]

A polydimethylsiloxane (PDMS) macroazoinitiator was synthesized from bis(hydroxyalkyl)‐terminated PDMS and 4,4′‐azobis‐4‐cyanopentanoic acid by a condensation reaction. The bifunctional macroinitiator was used for the block copolymerization of ethyl methacrylate (EMA) and 2‐(trimethylsilyloxy)ethyl methacrylate (TMSHEMA) monomers. The poly(DMS‐block‐EMA) and poly(DMS‐block‐TMSHEMA) copolymers thus obtained were characterized using Fourier transform infrared and ¹H NMR spectroscopy and differential scanning calorimetry. After the deprotection of trimethylsilyl groups, poly(DMS‐block‐HEMA) and poly(DMS‐block‐EMA) copolymer film surfaces were analysed using scanning electron microscopy and X‐ray photoelectron spectroscopy. The effects of the PDMS concentration in the copolymers on both air and glass sides of films were examined. The PDMS segments oriented and moved to the glass side in poly(DMS‐block‐EMA) copolymer film while orientation to the air side became evident with increasing DMS content in poly(DMS‐block‐HEMA) copolymer film. The block copolymerization technique described here is a versatile and economic method and is also applicable to a wide range of monomers. The copolymers obtained have phase‐separated morphologies and the effects of DMS segments on copolymer film surfaces are different at the glass and air sides. Copyright © 2010 Society of Chemical Industry     

Properties of PVA-AA cross-linked HEMA-based hydrogels

Poly(HEMA) hydrogel is usually prepared by using 1,1,1-trimethylol propane trimethacrylate and ethylene glycol dimethacrylate as the crosslinkers. Another method using PVA-AA (polyvinyl alcohol partially esterified with acryloyl chloride) as the cross linker is reported here. Two hydrogels, co-A1H9 and co-A2H8, were prepared by the polymerization of HEMA in the presence of 10% and 20% PVA-AA, respectively. The presence of PVA-AA reduced the water content from 32% to 25% in the resultant copolymer, whereas T_g did not change significantly. Co-A1H9 had an elastic modulus of 6.3 Mpa, which is much higher than 3.9 MPa and 3.7 MPa for poly(HEMA) and co-A2H8, respectively. The interfacial energies of poly(HEMA), co-A1H9 and co-A2H8 were calculated to be 0.52, 0.65 and 0.71 dyne/cm², respectively, whereas the fractional polarities of these three hydrogels were all about 0.74. Thus a HEMA-based hydrogel with surface properties similar to poly(HEMA) but with stronger mechanical strength was successfully prepared. This copolymeric hydrogel could provide a choice other than the conventionally cross linked poly(HEMA) for various applications.