氧抑制剂与分子流动性的关系:残余双键是影响初始粘度的函数

透明涂料的双重固化(热固化和UV固化)为层面涂装和汽车的更多特种部件的发展提供了巨大的发展前景。因为其可能解决紫外固化的屏蔽区的固化不完全的问题[1]。在先前的论文中,已经证实了UV光张度(辐射密度,I0)对暴露膜表面和丙烯酸酯中分子结构的双键转换的深层断面的氧抑制作用的影响[2～6]。近期的研究评价了具有不同玻璃化温度的固态聚合物基体对丙烯酸酯结构中双键转换的影响。探讨了UV固化配方和双重固化配方之间比较的一种直接判断的性能。研究中所使用的固态聚合物基体包括:聚甲基丙烯酸甲酯(PMMA,Tg114℃,平均重均分子质量 MW120000)和聚甲基丙烯酸丁酯(PBMA,Tg15℃,MW=337000)。通过改变单体和齐聚物混合物的分子质量的比以及固态聚合物基体的总含量,调整有氧存在或无氧存在的暴光时间(即固化速度)来进行研究工作,对于这个双重固化配方还用恒定的UV能量辐射评价了残余双键。用FTIR证实了剩余双键。讨论了紫外固化和双重固化配方的自游基迁移性和氧抑制作为配方体系粘度的功能函数。这些研究工作是基础性的而且是非常重要的。其目的是探索双重固化透明涂料的工业应用。     

Facile and efficient synthesis of hyperbranched polyesters based on renewable castor oil

Hyperbranched polyesters with thioether linkages were facilely prepared from methyl 10‐undecenoate, a castor oil‐derived renewable chemical. The monomer was obtained in excellent yield through thiol–ene click chemistry in the presence of catalytic amounts of photoinitiator under UV irradiation. Subsequent bulk polycondensation via a transesterification process catalyzed by Ti(OBu)₄, Sb₂O₃ or Zn(OAc)₂ gave hyperbranched polyesters with high molecular weights and unusual crystalline properties. The degree of branching in the range 0.45 ? 0.54 calculated from quantitative ¹³C NMR spectroscopy and low inherent viscosities of 0.16 ? 0.25 dL g^?1 strongly confirmed the hyperbranched structures of the resultant polymers. © 2012 Society of Chemical Industry     

Synthesis of new amphiphilic water‐stable hyperbranched polycarbosilane polymers

New amphiphilic hyperbranched polymers possessing hydrophobic skeletons and hydrophilic terminal groups have been prepared and characterized. The synthetic strategy involved the formation of a new stable matrix with aromatic units within a carbosilane backbone, as well as the use of a classical polycarbosilane matrix. Both of them with allyl groups on the surface have narrow polydispersity values. Molecular weight and polydispersity of the hyperbranched polymers were obtained using gel permeation chromatography with multi‐angle light scattering, and determination of the average number of functional groups present on the surface was achieved using ¹H NMR spectroscopy. The introduction of ionic groups was carried out via thiol–ene reactions with various thiol derivatives. The thermal properties of the polymers were also analysed using differential scanning calorimetry and zeta potential measurements. © 2013 Society of Chemical Industry     

Thermal polymerization of thiol–ene network‐forming systems

The thermal polymerization of a tetrafunctional thiol (PETMP) and divinyl ether (TEGDVE) was monitored by temperature‐ramping differential scanning calorimetry (DSC) and the effects of inhibitor type and concentration, oxygen inhibition and initiator type were studied. The incorporation of inhibitors was required to produce a stable system at room temperature. Butylated hydroxytoluene (BHT) inhibited polymerization at low temperatures, but was inefficient at high temperatures and polymerization rates, and hence BHT is an ideal stabilizer. In contrast, a nitroxide inhibitor (NO‐67) was a very effective inhibitor and no polymerization occurred until all of the nitroxide was depleted. The presence of oxygen retarded the onset of polymerization but did not change the final conversion significantly. Polymerization with initiators having higher half‐life temperatures shifted the DSC peak to higher temperature because the rate of initiator decomposition and thus initiation was slower. Rheological investigations of the cure at different temperatures revealed that the gel time decreased significantly with increasing cure temperature, and the calculated apparent activation energy for PETMP/TEGDVE was 54 kJ mol^?1. Dynamical mechanical thermal analysis of the cured material was undertaken and frequency‐superposed results revealed that the glass transition region of PETMP/TEGDVE/azobisisobutyronitrile was much narrower than that of free‐radically cured dimethacrylate, but was similar to that of an epoxy resin cured with an aromatic diamine. This behaviour could be attributed to PETMP/TEGDVE network homogeneity, or to the less constrained crosslinks in the PETMP/TEGDVE network. Copyright © 2007 Society of Chemical Industry     

A novel method for preparation of epoxy resins using thiol–ene click reaction

Epoxy resins (EPs) have a wide range of applications due to their remarkable performances. A major issue about them is the associated serious environmental pollution and high manufacturing cost because of the tedious synthetic procedure and the large amount of organic solvents used in production. Here, we report a facile, highly efficient approach to addressing these challenges using thiol–ene click reaction. The new synthesis process is based on mass‐produced materials including triols, diols, mercaptopropionic acid and glycidyl methacrylate and involves only two steps, that is, esterification and thiol–ene click reaction. Three types of high purity sulfur‐containing EPs are synthesized at high yields. The chemical structures and molecular weights of the newly synthesized EPs were characterized by Fourier translation infrared spectroscopy, ¹H‐NMR and matrix‐assisted laser desorption/ionization time of flight mass spectrometry. Using the methyl nadic anhydride as crosslinker, these resins have shown excellent heat‐resistance due to the absence of hydroxyl groups. They demonstrate high thermal decomposition temperatures, showing no dehydration decomposition at 260°C and therefore are suitable for applications as solvent‐free resins. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42316.     

Preparation of Biomolecule Microstructures and Microarrays by Thiol–ene Photoimmobilization

A mild, fast and flexible method for photoimmobilization of biomolecules based on the light‐initiated thiol–ene reaction has been developed. After investigation and optimization of various surface materials, surface chemistries and reaction parameters, microstructures and microarrays of biotin, oligonucleotides, peptides, and MUC1 tandem repeat glycopeptides were prepared with this photoimmobilization method. Furthermore, MUC1 tandem repeat glycopeptide microarrays were successfully used to probe antibodies in mouse serum obtained from vaccinated mice. Dimensions of biomolecule microstructures were shown to be freely controllable through photolithographic techniques, and features down to 5 μm in size covering an area of up to 75×25 mm were created. Use of a confocal laser microscope with a UV laser as UV‐light source enabled further reduction of biotin feature size opening access to nanostructured biochips.     

UV curable soybean‐oil hybrid systems based on thiol‐acrylate and thiol‐ene‐acrylate chemistry

In this study, epoxidized soybean oil was modified to prepare acrylated epoxidized soybean oil (AESO) and vinyl/acrylate ended soybean oil (VASO), which were blended with mercaptopropyl polyhedral oligomericsilsequioxane (POSS‐SH) to prepare UV curable thiol‐acrylate and thiol‐ene‐acrylate hybrid coatings. Photopolymerization processes of the coatings were measured and the results showed that addition of POSS‐SH obviously increased the conversion of double bond. The physical and mechanical properties of all cured samples were investigated, which indicated that the pencil hardness, tensile strength, and fracture toughness were significantly improved by POSS‐SH. Moreover, with increasing POSS‐SH content, the water contact angles of cured samples were increased, and the water resistance was greatly improved. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42095.     

紫外光固化体系的研究进展

综述了紫外光固化体系,包括自由基紫外光固化体系、阳离子紫外光固化体系、自由基-阳离子混杂光固化体系和双重固化体系的研究进展。     

混杂光固化体系的原理及应用

混杂光固化或双重固化是指在同一体系中采用两种或两种以上不同类型的聚合反应来使体系固化的方法,它是原位改性高分子的一种新方法,混杂光固化体系包括自由基－阳离子混杂光固化体系,自由基－缩聚混杂体系和自由基－自由基混杂体系等,本文综述了混杂光固化体系的原理及其应用。     

Bicyclo‐orthoester as a low‐shrinkage additive in cationic UV curing

A commercially available bicyclo‐orthoester (BOE) was used as low‐shrinkage additive for cationic UV curing of epoxy resins. A high reactivity of BOE by ring‐opening homopolymerization has been observed under cationic UV curing conditions. The BOE and trimethylolpropane triglycidyl ether monomers are compatible and give rise to a cured copolymeric network, under UV irradiation, with a flexibilization increase by increasing the BOE content in the photocurable formulation. Shrinkage after photopolymerization shows a linear reduction by increasing the BOE content in the photocurable formulation; a volume expansion upon polymerization is reached in the presence of 50 wt% of the additive. Copyright © 2007 Society of Chemical Industry     

紫外光固化EA树脂的研制

环氧树脂和丙烯酸在适宜条件下合成EA树脂。讨论了各种反应条件对EA树脂性能的影响。确定了最佳工艺条件 :催化剂A用量 1% ,阻聚剂B用量 1‰～ 3‰ ,在 10 0℃滴加丙烯酸 1 0h～ 1.5h ,滴加完后在 110℃反应约 0 5h ,丙烯酸与环氧树脂的摩尔比为 1 0 4∶1。     

Study on the volumetric expansion of benzoxazine curing with different catalysts

A systematic investigation on the volumetric expansion of four benzoxazine systems, which are benzoxazine, benzoxazine/tertiary amine, benzoxazine/organic acid, and benzoxazine/epoxy resin/tertiary amine, was done. By using gravitometric and dilatometric methods, etc., studies on volumetric shrinkage, isothermal cure shrinkage, and density versus cure time plots were done. The cure reactions of these benzoxazines were carried out at 140 and 160°C. The results show that all benzoxazine systems exhibit apparent volumetric expansion after polymerization, that is, the densities of monomers are larger than are those of polymers at room temperature. But, meanwhile, they exhibit volumetric shrinkage while curing isothermally. The results also show that the higher the cure temperature is, the larger the cure shrinkage of the benzoxazines will be and that the extent of the cure shrinkage of the benzoxazines with the aid of catalysts is larger than is that of thermal polymerization systems. The reason for this is that, accelerated by catalysts, the polymerization rate become faster and the extent of polymerizatiom becomes larger. It is obvious that catalysts can make a notable impact on the cure reaction of benzoxazines. Therefore, the dimension of the volumetric expansion of benzoxazine is associated with its polymerization mechanism, molecular structure, and extent of polymerization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1107–1113, 2002; DOI 10.1002/app.10267     

A very simple empirical kinetic model of the acid‐catalyzed cure of urea–formaldehyde resins

The hot pressing operation is the final stage in MDF (medium density fiberboard) manufacture; the fiber mat is compressed and heated up to promote the cure of the resin. The aim of the investigations is to study the curing reactions of UF (Urea–Formaldehyde) resins as commonly used in the production of MDF, and to develop a simplified kinetic model. This investigation has combined Raman spectroscopy to study the reaction cure and ¹³C‐NMR for the quantitative and qualitative characterization of the liquid and still uncured resin. Raman spectroscopy was found very interesting for the study of the resin cure and permitted to obtain kinetic data as the basis for a simple empirical model, considering a homogeneous irreversible reaction of a single kind of methylol group and ureas with rate constants depending on their degree of substitution. Although these results can provide a better understanding of the composition and the cure of an UF resin, several issues remain open, such as the influence of the reversibility of the reactions taking place during the curing process as well as the possible formation of cyclic groups in the resin. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5977–5987, 2006     

Photopolymerization kinetics,photorheology and photoplasticity of thiol–ene–allylic sulfide networks

BACKGROUND: Thiol–ene networks are of interest due to their facile photopolymerization and their open network structure. In this work, an allylic disulphide divinyl ether monomer is reacted with tetrathiol and divinyl ether monomers, which allows the network structure to permanently change in shape if stressed while under irradiation. We also study the photo‐differential scanning calorimetry (DSC) kinetics and photorheology during cure and the dynamic mechanical properties after cure. RESULTS: The heat of polymerization is similar for the thiol–ene systems and suggests ca 80% conversion of the vinyl ether groups. An increase in the initiator concentration increases the photocure rate as expected. The activation energy for photopolymerization is 7.6 kJ mol^?1. DSC and rheometry studies show that the polymerization kinetics is slowed by the addition of the allylic disulfide divinyl possibly due to the formation of less reactive radicals. However, as shown by dynamic mechanical thermal analysis, the network structure is not changed very much by addition of this monomer. If radicals are generated by irradiation of a photoinitiator in the network while a stress is being applied, the polymer will permanently deform depending on the fraction of 2‐methylenepropane‐1,3‐di(thioethyl vinyl ether) in the network, due to a bond interchange reaction. CONCLUSION: The rate of thiol–ene reaction is slowed by the addition of the allylic disulfide divinyl ether. Photoplasticity is observed in the networks containing the allylic disulfide groups. Further work is required to optimize the extent of photoplasticity in these systems. Copyright © 2007 Society of Chemical Industry     

Facile design of biomaterials by ‘click’ chemistry

The advent of the so‐called ‘click chemistry’ a decade ago has significantly improved the chemical toolbox for producing novel biomaterials. This review focuses primarily on the application of Cu(I)‐catalysed azide–alkyne 1,3‐cycloadditon in the preparation of numerous, diverse biomaterials and biomedical materials and concepts. In addition, the thiol–ene ‘click’ reaction is addressed in the same manner, and the possibility of using both click reactions orthogonally is highlighted. A strategy for the preparation of novel intriguing poly(ε‐caprolactone)‐based nanobiomaterials by orthogonal click chemistry is elaborated. The present state of creating functional and biologically active surfaces by click chemistry is presented. Finally, conducting surfaces based on an azide‐functionalized polymer with prospective biological sensor potential are introduced. Copyright © 2012 Society of Chemical Industry     

Kinetic rate equation combining ultraviolet‐induced curing and thermal curing. I. Bismaleimide system

A novel and general kinetic rate equation combining ultraviolet‐induced (UV‐induced) curing and thermal curing was successfully derived from the conventional thermal‐kinetic rate equation. This proposed novel kinetic rate equation can be applicable to the curing system either simultaneously or individually by UV‐induced and thermal cure methods. This general kinetic rate equation is composed of the reaction order n, activation energy E_a, curing temperature T, energy barrier of photoinitiation E_Q, intensity of UV radiation Q, concentration of photoinitiator [I], and a few other parameters. The proposed equation was supported by experimental data based on the curing systems of 4,4′‐bismaleimidodiphenylmethane (BMI) and 2,2‐bis(4‐(4 maleimido phenoxy) phenyl propane (BMIP). The BMI and BMIP systems were isothermally cured at various temperatures, or simultaneously cured with varying intensity of UV radiation (wavelength 365 nm). Conversion levels for the various cured samples were subsequently measured with a FTIR spectrometer. The reaction order n = 1.2, activation energy E_a = 40,800 J/mol, and E_Q = 7.5 mW/cm² were obtained for curing BMI system. The reaction order n = 1.3, activation energy E_a = 53,000 J/mol, and E_Q = 9.1 mW/cm² were obtained for curing BMIP system. The values of n and E_a in the same curing system (BMI or BMIP) are irrespective of the curing method (either simultaneously or individually by UV‐induced and thermal cure methods). The salient results of this study show that UV radiation only enhances the initiation rate and UV ration do not influence the activation energy E_a. The experimental results are reasonably well represented by these semi‐empirical expressions.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Two-step curing processes for coating application

Two novel two-stage cure processes will be described, both involving oxetane chemistry. In both processes, the two consecutive cure processes are completely separated from one another.