Role of Functional Groups in the Monomer Molecule on the Radical Polymerization in the Presence of Graphene Oxide. Polymerization of Hydroxyethyl Acrylate under Isothermal and Non-Isothermal Conditions

Functional groups in a monomer molecule usually play an important role during polymerization by enhancing or decreasing the reaction rate due to the possible formation of side bonds. The situation becomes more complicated when polymerization takes place in the presence of graphene oxide since it also includes functional groups in its surface. Aiming to explore the role of functional groups on polymerization rate, the in situ bulk radical polymerization of hydroxyethyl acrylate (HEA) in the presence or not of graphene oxide was investigated. Differential scanning calorimetry was used to continuously record the reaction rate under both isothermal and non-isothermal conditions. Simple kinetic models and isoconversional analysis were used to estimate the variation of the overall activation energy with the monomer conversion. It was found that during isothermal experiments, the formation of both inter- and intra-chain hydrogen bonds between the monomer and polymer molecules results in slower polymerization of neat HEA with higher overall activation energy compared to that estimated in the presence of GO. The presence of GO results in a dissociation of hydrogen bonds between monomer and polymer molecules and, thus, to higher reaction rates. Isoconversional methods employed during non-isothermal experiments revealed that the presence of GO results in higher overall activation energy due to the reaction of more functional groups on the surface of GO with the hydroxyl and carbonyl groups of the monomer and polymer molecules, together with the reaction of primary initiator radicals with the surface hydroxyl groups in GO.     

Synthesis of polyheterocycles on the basis of poly-functional monomers and study of their characteristics

Application of polyfunctional monomers in the course of polycondensation allows to synthesize different types of polymers using different activity of functional groups. It is possible in this case to vary to a large extent the characteristics of the obtained polymers. The presence of functional groups of different activity in one monomer also allows to modify it by introduction of new fragments for subsequent use in polycondensation or polymerization reactions. The abovementioned is confirmed by the example of using trimellitic anhydride and a number of alicyclic tetracarbonic dianhydrides. Trimellitic anhydride is directly used for synthesis of polymers and also modified for preparation of new derivatives. The perspective of using alicyclic tetracarbonic dianhydrides for synthesis of heterocycles has been shown. Varying the monomer nature and conditions of a polycondensation reaction, polymers with different specific characteristics have been obtained: heat-resistant, high- and low-fusible, soluble, incombustible, film-forming, fiber-forming, binding for glass-plastics.     

Functionalization of poly(<Emphasis Type="Italic">N</Emphasis>-ethylmethacrylamide) thermosensitive particles by phenylboronic acid

The synthesis of poly(N-ethylmethacrylamide) (NEMAM) thermosensitive particles functionalized with phenylboronic acid (PhBA) groups has been performed by emulsion/precipitation polymerization of NEMAM in water at 90 °C, using ethylene glycol dimethacrylate (EGDMA) as an hydrophobic crosslinker, phenylboronic acid methacrylamide (PhBAMA) as a functional monomer, and potassium persulfate (KPS) as an initiator. The influences of the PhBAMA concentration and mode of monomer addition (batch or shot-growth processes) have been examined both on the polymerization kinetics and on the physicochemical and colloidal properties of the final particles. Results have been discussed according to the ionogenic and hydrophobic nature of the functional monomer. We have directly and clearly provided evidence that PBA was successfully incorporated at the particle surface by using ESCA analysis, especially when using a shot-growth process, a result that was indirectly confirmed by investigating the electrophoretic mobility behavior of the various latexes as a function of pH.     

Benzophenone-initiated grafting photopolymerization of acrylic acid on the surface of polyethylene from the monomer aqueous solution without its deaeration

The photoinduced grafting polymerization of a functional monomer (acrylic acid) is performed on the surface of a polymeric material (polyethylene film) from a nondeaerated aqueous solution of the monomer with the use of a water-insoluble photoinitiator (benzophenone). According to the developed method, the photoinitiator is first deposited on the surface of the polyethylene film from solution in a volatile solvent; then, the surface of the film is covered with a layer of the nondeaerated aqueous solution of the monomer, over which a quartz plate or the second polyethylene film is placed, and the resulting sandwich is exposed to UV radiation. This method is highly efficient when the thickness of the monomer-solution layer is less than 100 ??m. Owing to the small thickness of the monomer solution layer and the absence of the inflow of atmospheric oxygen, molecular oxygen that is initially contained in the monomer solution is rapidly consumed in photooxidation reactions occurring on the surface of the substrate polymer; therefore, molecular oxygen insignificantly affects the efficiency of grafting polymerization.     

Preparation of highly sulfonated polystyrene model colloids

Previous attempts to prepare monodisperse styrene/sodium styrene sulfonate copolymer latexes by batch, seeded, and semicontinuous emulsion polymerization were unsuccessful at high concentrations of the functional comonomer. Broad, and sometimes bimodal, size distributions, and large amounts of water soluble homopolymer were obtained. After removal of free monomer, solute and adsorbed homopolymer and copolymer, the overall incorporation of the functional comonomer was found to be low. To overcome these problems, a two stage “shot-growth” or in situ seeding technique was developed. A first stage copolymerization was carried out with a low concentration of sodium styrene sulfonate: the purpose of the functional comonomer was to enhance the stability and regulate the size of the seed particles. When this reaction had reached high conversion (> 90%), a second stage monomer mixture was added. The ratio of styrene to sodium styrene sulfonate in this mixture determined the final surface charge density. The mechanism by which the NaSS is incorporated in the polymer particles is considered to be by solution copolymerization with solute styrene monomer to form surface active oligoradicals. These radicals adsorb on the particle surface, initiate polymerization and become inextricably bound, preventing their transfer back to the aqueous phase. By this means, it was possible to vary independently the particle size and surface charge density. High concentrations of functional comonomer could be polymerized without undue wastage (incorporations were only slightly less than 100%) or loss of monodispersity. In extreme cases, the area per functional group fell below the theoretical minimum, indicating considerable hydration of the surface layers.     

Synthesis of high-solid,low-viscosity hydroxy acrylic resin modified with TBCHA

Hydroxyl acrylic resin using 4-tert-Butylcyclohexyl acrylate (TBCHA) as functional monomer has been synthesized via solution polymerization technique. Most critical experimental conditions have been optimized first by mixture experimental design methodology prior to real experiment operations. Afterward high-solid and low-viscosity hydroxy acrylic resin was synthesized under the optimized experimental conditions. According to a series of characterization methods including rheology, IR, TGA, addition of functional monomer, TBCHA, combined with optimized experiment conditions can reduce the viscosity of as-synthesized resin significantly at high solid content.     

Molecularly imprinted adsorbents for positional isomer separation.

2,4-Dihydroxybenzophenone (2,4-DHB) imprinted polymers were synthesized by surface imprinting technique, using allyl alcohol as the functional monomer. The polymers showed a very high selectivity for 2,4-DHB when compared with various positional isomers such as 2-HB, 2,2'-DHB, 4,4'-DHIB and 4,4'-DMB. Solvents were found to affect the selectivity as well as sorption capacity in the case of surface imprinted polymers. The selectivities decreased drastically when the imprint cavity was blocked. This validated the importance of the cavity and the rebinding interactions in governing the selectivity in the case of MIPs. The surface imprinted polymers also showed a high selectivity under non-equilibrium conditions thereby making them suitable adsorbents for industrial separations.     

Capillary electrochromatographic separation of amino acid enantiomers with molecularly imprinted polymers as chiral recognition agents

The use of molecularly imprinted polymers polymerized in a capillary for the separation of amino acid enantiomers by electrochromatography is described. The substrate-selective polymers were prepared by using l-phenylalanine anilide as print molecule and methacrylic acid as the functional monomer. The treatment of the inside surface of the capillary, the composition of the polymer and the electrochromatographic running conditions were investigated. This preliminary report demonstrated a novel and simple method for capillary electrochromatographic separations of amino acid enantiomers using molecularly imprinted polymers. Received: 9 April 1996 / Revised: 8 August 1996 / Accepted: 8 August 1996     

表面接枝分子印迹聚合物微球的合成及评价

将聚苯乙烯-二乙烯苯微球表面功能基化, 引入引发转移终止剂(initiator-transfer-terminator agent, iniferter), 以活性自由基聚合方式研究了球形树脂表面合成印迹聚合物的方法. 在紫外光引发下, 以左旋麻黄碱为印迹分子, 甲基丙烯酸为功能单体, 在接枝Iniferter后的微球表面进行分子印迹聚合物接枝实验, 并使用不同的反应条件, 探讨了表面接枝印迹层微球制备条件对于识别能力的影响. 平衡吸附的结果表明, 表面接枝聚苯乙烯-二乙烯苯微球对于印迹分子具有亲和能力及选择性, 其识别能力来自于印迹得到的识别位点.     

Novel molecularly imprinted microsphere using a single chiral monomer and chirality-matching (S)-ketoprofen template

We designed and synthesized a cinchonine derivative to be used as a novel chiral monomer. It was employed in a dual role of functional monomer and cross-linking monomer, displaying multi-binding sites for the template (S)-ketoprofen. Monodisperse molecularly imprinted core-shell microspheres were prepared using surface imprinting method on silica gel. The results show a substantial synergistic effect in the enantioselective recognition, confirming our initial hypothesis. Computational simulation of the monomer and template pre-arrangement strongly supports our proposed chiral recognition mechanism for the imprinted microspheres.     

Selective surface modification technique for improvement of chromatographic separation selectivity for sugar derivatives.

Highly cross-linked macroporous polymers were prepared utilizing ethylene dimethacrylate as a cross-linking agent, in the presence or absence of methyl-alpha-D-glucoside as a kind of template molecule with methacrylic acid as a functional monomer. After the preparation of the polymers, we applied a high temperature to the cross-linked polymers to study the changes of adsorption properties of the polymers for sugar derivatives including the template molecule utilized. Interestingly, the heat treatment up to 250 degrees C afforded improvement of relative adsorption affinity for several sugar derivatives including the template molecule, while heat treatment up to 150 degrees C did not afford those improvements. The detailed studies including polymers prepared using acrylic acid as a functional monomer instead of methacrylic acid prove that temperatures higher than the Tg temperature of the polymer derived from a functional monomer such as methacrylic acid and higher than the melting point (mp) of the sugar template are necessary to afford the observed improvement of relative affinity based on the surface modification effects through the heat treatment to cross-linked polymers.     

Grafting of amino functional monomer onto initiator-modified polystyrene particles

Polystyrene nanoparticles with grafted chains of an amino functionalized polymer were prepared by a two-step polymerization process. In the first step, the polystyrene seed particles were synthesized by the conventional batch emulsion polymerization using terpolymer HAS (hydroperoxide monomer, acrylic acid, and styrene) as a surface-active initiator. The surface of the obtained particles contains carboxyl groups, which are responsible for the latex stability, and residual undecomposed hydroperoxide groups. Therefore, in the second step, an amino functional monomer was grafted onto the hydroperoxide modified polystyrene particles by a "grafting from" approach. X-ray photoelectron spectroscopy, NMR, and scanning electron microscopy were used to examine the surface of the amino functionalized particles. The amount of incorporated amino groups onto the particles was determined by fluorescenometric titration. In general, the number of amino groups on the particle surface increased with the increase of the functional monomer content in the reaction mixture. The incorporation of the functional monomer was also confirmed by electrophoretic measurements. Final particles possess amphoteric character due to the presence of amino and carboxyl groups on the surface. Adsorption of human immunoglobulins G onto the amino functionalized particles was studied as a function of pH and ionic strength. The covalent binding of human IgG was performed using the glutaraldehyde preactivation method. The immunoreactivity of the latex-IgG complex was examined by the latex agglutination test.     

二苯甲酰-D-酒石酸分子印迹整体柱的制备及其色谱性能

采用紫外光谱法选择丙烯酰胺为功能单体,以二苯甲酰-D-酒石酸(D-DBTA)为模板分子,丙烯酰胺为功能单体,二甲基丙烯酸乙二醇酯为交联剂,甲苯和十二醇为混合致孔剂,用原位分子印迹技术,合成了D-DBTA分子印迹整体聚合物。在优化色谱条件的基础上,25min内基本实现了DBTA消旋体的手性分离,分离度达1.25。对色谱分离过程中的热力学进行分析,在所考察的温度范围内,色谱分离存在两种不同的热力学过程,且两者与范特霍夫方程能够很好地吻合。在这两种热力学过程的转换温度处,分离因子α达最大值。     

A humidity blocker approach to overcoming the humidity interference with cationic photopolymerization

A humidity blocker approach to overcoming the humidity interference with cationic photopolymerization is proposed and validated. Environmental humidity is one of the major interfering factors in cationic photopolymerization, and cationic photopolymerization is found to be inhibited by high humidity. When curing cycloaliphatic epoxide based cationic UV curable materials flexibilized by various reactive diluents under different humidity conditions, it was found that the more hydrophobic materials exhibited higher monomer conversion under higher humidity. To obtain cationic UV curable materials that are less influenced by humidity, a humidity blocker approach was proposed and monomer conversion of materials containing both hydroxy‐functional reactive diluents and epoxy‐siloxane were examined using real‐time FTIR. The hydroxy‐functional reactive diluents act as an internal hydroxyl source that enhances monomer conversion through chain transfer mechanism, and the hydrophobic epoxy‐siloxane acts as a humidity blocker, mitigating the inhibiting effects of humidity. Cationic UV curable materials with an optimized combination of these two components exhibited higher and more consistent monomer conversion under a range humidity conditions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4344–4351, 2008     

温度及pH敏感N-异丙基丙烯酰胺/β-环糊精水凝胶的合成与性能研究

用顺丁烯二酸酐 (MAH)对具有分子包结能力的 β 环糊精 (β CD)进行化学改性 ,合成出了丁烯二酸单酯化 β CD单体 (MAH β CD) .通过氧化还原自由基引发MAH β CD与N 异丙基丙烯酰胺 (NIPA)聚合 ,合成出含 β CD结构单元的新型水凝胶 .用核磁共振、红外光谱及元素分析对MAH β CD单体及共聚物的结构和组成进行了表征 .溶胀研究结果表明 ,该水凝胶具有较好的pH、温度及离子强度敏感性 ;并且水凝胶在较高羧基(—COOH)含量和弱碱环境中 ,仍能表现出明显的温敏性     

Synthesis and characterization of polyfunctional crosslinking agents for cyanate resins

An efficient crosslinking monomer for a mixed cyanate/epoxy resin system, bisphenol-A-monocyanate monoglycidyl ether 3 , has been synthesized and characterized. The intermediate compound, the monoglycidyl ether of bisphenol-A 2 , was also isolated and purified by extraction and chromatographic separation using a silica gel column. The cyanate functional group in the crosslinking monomer 3 can be cured easily by heat to form a triazine structure 8 , but the epoxy functional group in the crosslinking monomer 3 can not be cured without affecting the cyanate group because the latter is more reactive both under heat and basic conditions. A practical approach for the application of the crosslinking monomer 3 is discussed and tested. Most interestingly, under heat curing, a very tough and strong resin material was produced from this crosslinking mixed resin mixture. By using a secondary amine, diethylamine, as a curing agent, the cyanate groups in the crosslinking monomer 3 react to form the structures 11 or 12 , depending on the molar ratio of monomer 3 to diethylamine. A bifunctional crosslinking agent for a mixed cyanate (thermoset) and polyolefin (thermoplastic) resin system, 2-allylphenyl cyanate 16 , has also been synthesized and characterized. Like 3 , 2-allylphenyl cyanate 16 easily forms the crosslinking triazine compound 17 upon heating. 17 is a crystalline solid with mp = 110–111°C. As a crosslinking agent, 2-allylphenyl cyanate 16 reacts not only with itself, but also with other cyanates to form heterogeneous triazine rings, exemplified by triazines 18 and 19 . Even though it does not self polymerize through the allyl double bond, it can copolymerize with an other olefinic monomer, such as methyl methacrylate, to form a crosslinked and insoluble polymer. © 1995 John Wiley & Sons, Inc.     

Water-compatible molecularly imprinted polymers for efficient direct injection on-line solid-phase extraction of ropivacaine and bupivacaine from human plasma

Two novel molecularly imprinted polymers (MIPs) selected from a combinatorial library of bupivacaine imprinted polymers were used for selective on-line solid-phase extraction of bupivacaine and ropivacaine from human plasma. The MIPs were prepared using methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linking monomer and in addition hydroxyethylmethacrylate to render the polymer surface hydrophilic. The novel MIPs showed high selectivity for the analytes and required fewer and lower concentrations of additives to suppress non-specific adsorption compared with a conventional MIP. This enabled the development of an on-line system for direct extraction of buffered plasma. Selective extraction was achieved without the use of time-consuming solvent switch steps, and transfer of the analytes from the MIP column to the analytical column was carried out under aqueous conditions fully compatible with reversed-phase LC gradient separation of analyte and internal standard. The MIPs showed excellent aqueous compatibility and yielded extractions with acceptable recovery and high selectivity.     

Facile immobilization of biomolecules onto various surfaces using epoxide-containing antibiofouling polymers

The surface modifications of plastic or glass substrate and the subsequent immobilization of biomolecules onto the surfaces has been a central feature of the fabrication of biochips. To this end, we designed and synthesized new epoxide-containing random copolymers that form stable polymer adlayers on plastic or glass surface and subsequently react with amine or sulfhydryl functional groups of biomolecules under aqueous conditions. Epoxide-containing random copolymers were synthesized by radical polymerization of three functional monomers: a monomer acting as an anchor to the surfaces, a PEG group for preventing nonspecific protein adsorption, and an epoxide group for conjugating to biomolecules. Polymer coating layers were facilely formed on cyclic olefin copolymer (COC) or glass substrate by simply dipping each substrate into a solution of each copolymer. The polymer-coated surfaces characterized by a contact angle analyzer and X-ray photoelectron spectroscopy (XPS) showed very low levels of nonspecific immunoglobulin G (IgG) adsorption compared to the uncoated bare surface (control). Using a microcontact printing (μCP) method, antibodies as representative biomolecules could be selectively attached onto the copolymers-coated glass or COC surface with high signal-to-noise ratios.     

Chemical graft polymerization of sulfobetaine monomer on polyurethane surface for reduction in platelet adhesion

Surface modification is an effective way to improve the hemocompatibility and remain bulk properties of biomaterials. Recently, polymer tailored with zwitterions was found having good blood compatibility. In this study, the zwitterionic monomer of sulfobetaine was graft polymerized onto polyurethane (PU) surface in a three-step heterogenous system through the vinyl bonds of acrylic acid (AA) or hydroxyethyl methacrylate (HEMA), which was immobilized with hexamethylene diisocyanate (HDI) beforehand. First, PU was activated with isocyanate groups using HDI as coupling agent. Second, AA or HEMA was introduced through reaction of AA or HEMA with NCO groups bonded on PU surface. Last, zwitterionic monomer of sulfobetain was graft polymerized with vinyl group of AA or HEMA using AIBN as polymerization initiator. The reaction process was monitored with ATR-IR spectra and XPS spectra. Variation of graft yield with temperature and monomer feed concentration was investigated and feasible conditions were optimized. The wettability of films was investigated by water contact angle measurement and water absorbance. Platelet adhesion experiment was conducted as a preliminary test to confirm the improved blood compatibility of PU. The number of platelets adhering to PU decreased greatly comparing with the originals after 1 and 3 h of contact with human plate-rich plasma (PRP).     

Deposition characteristics of ureido silane ethanol solutions onto E-glass fibres

The determination of the adsorption and the deposition characteristics of a silane monomer, which does not hydrolyse until it contacts the glass surface can be done by examining the effect of ultra dry solvent carriers. Most of the publications to date concentrate on amine and vinyl silanes. Many industrial processes use silanes with alternative organic functional groups, this study examines an industrial silane monomer with ureido functionality. The determination of how these monomeric, unhydrolysed silane solutions deposit, will improve our knowledge of the deposition behaviour of the much more complicated heterogeneous aqueous solutions. We have shown using diffuse reflectance Fourier transform infra red (DRIFT) how ureido silane deposition from ethanol results in the silane bonding in the OCH₃ down orientation, with the ureido amine functions free for reaction with the polymer matrix. Furthermore, treatment with a series of solvents having solubility parameters which match (a) that of the unhydrolysed silane monomer and (b) that of the partially hydrolysed silane monomer can remove different fractions of the deposited silane and result in a certain amount of reorientation of the loosely bound physisorbed layers. X-ray photoelectron spectroscopy (XPS) results show that the silane was deposited in patches. Ultimately, precise control of the deposition conditions will determine the orientation of the silane monomer.