Crosslinking reactions and swelling behavior of matrices based on N-acryloyl-TRIS(hydroxymethyl)aminomethane

Summary In this study, new hydrogels in rod shape were prepared from N-acryloyl-TRIS(hydroxymethyl)aminomethane (NAT) using ethylene glycol dimethacrylate (EGDMA) or N,N’methylenebisacrylamide (BIS) as crosslinking agent, dimethylformamide (DMF) as solvent and benzoyl peroxide (BPO) as initiator. In most cases, 2-hydroxyethyl methacrylate (HEMA), acrylamide (Aam) or acrylic acid (Aac) were used as co-monomers. The polymeric matrices obtained by free radical polymerization exhibited different properties by changing crosslinker, crosslinker concentration, co-monomer and initial NAT/co-monomer mole ratio. Besides, hydrogels from HEMA, Aam and Aac with BIS in absence of NAT were prepared under the same experimental reaction conditions in order to compare the properties of these products with those synthesized from NAT and the respective co-monomers. Some of the final products were selected to perform urea release assays, conducted through swelling-controlled release. Urea was chosen as “model” plant fertilizer agent.     

Synthesis and characterization of star-like microgels by one-pot free radical polymerization

A one-pot free radical polymerization process was used to prepare methyl acrylate/ethylene glycol dimethacrylate (MA/EGDMA) and methyl methacrylate/ethylene glycol dimethacrylate (MMA/EGDMA) polymers. The role of monomer and crosslinker reactivity ratios in producing different network structures was demonstrated. While both systems produced branched polymers that exhibited low intrinsic viscosities with little variation across a wide range of molecular weights, the star-like microgels formed between a less reactive monomer (MA) with a more reactive crosslinker (EGDMA) gave lower bulk solution viscosities than the more statistical polymers formed between similarly reactive monomers and crosslinkers (MMA and EGDMA). This paper presented a simple and cost-effective synthetic route for the production of polymers with high molecular weight and low viscosity with considerable potential for industrial-scale processing.     

Enhanced piezoresistance repeatability of carbon nanotube/silicane composites achieved using radiation-induced graft polymerization

Photo-activated removable acrylic pressure-sensitive adhesives (PSAs) were prepared by mixing a preformed polyacrylate resin with a multifunctional crosslinker, such as ethylene glycol dimethylacrylate (EGDMA), bisphenol A ethoxylate diacrylate (BAED), or trimethylolpropane triacrylate (TMPTA), and followed by a UV-curing process after film coating. The UV-curing process extensively increases the cohesive strength of PSA by increasing its molecular chain length, and the PSA can be removed from the substrate cleanly. The release of the PSA film can also be set to a requested time by applying a UV-curing process. It is shown that certain recipes with a combination of crosslinker and UV light showing excellent removability, such as using BAED with Irgacure 907, or EGDMA with Darocur 1173.     

多元共聚高吸油树脂合成及性能研究

以(甲基)丙烯酸酯类、苯乙烯为主要共聚单体,双甲基丙烯酸乙二醇酯(EGDMA)、二乙烯基苯(DVB)等为交联剂,采用悬浮共聚工艺合成了一系列高吸油树脂.研究了树脂共聚单体组成、丙烯酸单体链长、交联剂种类、交联度、引发剂量以及聚合工艺等因素对吸油树脂吸油量等性能的影响.结果表明:采用EGDMA交联时以丙烯酸十四酯的效果最佳,采用DVB交联时以丙烯酸十二酯效果最佳;交联剂种类及交联度大小对树脂吸油性能及树脂形态有明显影响;树脂交联度的大小明显影响树脂共聚物的转化率与可溶性分率,也明显影响树脂产品的收率.在最佳合成条件下制备的高吸油树脂具有较佳的吸油性能,对甲苯的吸附量可达17.32 g/g树脂.     

Polymer phase transition in n‐lauryl methacrylate monoliths

Monolithic materials prepared from a mixture of n‐lauryl methacrylate (LMA) and ethylene glycol dimethacrylate (EGDMA) dedicated to nano‐liquid chromatography separation were synthesized using in situ UV polymerization in 75 µm inner diameter capillary tubing. A mixture of cyclohexanol and ethylene glycol was used as a porogen to control porosity. While the preparation conditions yielded satisfactory analytical results, values of pertinent parameters turned out to be critical for obtaining columns with efficient separation. In particular, the impact of two key parameters was studied here in an attempt to identify optimal preparation conditions: (a) different concentrations of the crosslinker EGDMA and (b) different porogen compositions while the monomer to porogen ratio was kept constant. Resulting monolithic phases were characterized in terms of permeability, mean pore diameter and swelling using three different eluents (water, acetonitrile and a mixture at maximum viscosity). First, the LMA/EGDMA monolithic phases present peculiar morphology and hydrodynamic properties for 37% by weight of EGDMA, as reflected by the peak observed for their permeability and mean pore diameter. Swelling experiments revealed the coexistence of two phases in the monolithic structure: a highly crosslinked rigid phase which was insensitive to swelling in the presence of solvent and a weakly crosslinked flexible phase exhibiting significant swelling, with a transition to such a biphasic behavior taking place at 37% by weight of EGDMA. The effects of porogen composition and network swelling properties are presented based on a combination of the Flory ? Huggins theory of isotropic mixing in polymer solutions and the Flory ? Rehner theory of rubber elasticity in the affine network approximation. © 2016 Society of Chemical Industry     

Synthesis and properties of oil absorption resins filled with polybutadiene

Polybutadiene (PB) is used to fill an oil absorption resin as a physical crosslinker to construct a kind of 3‐dimensional network with a high degree crosslinking and low crosslink density. A series of acrylic resin particles with various compositions are prepared by suspension polymerization, using benzoyl peroxide (BPO) as an initiator and ethylene glycol dimethacrylate (EGDMA) as a chemical crosslinker. The effects of the polymerization temperature, initiator concentration, monomer feed ratio, and chemical and physical crosslinker concentrations on the oil absorbency and gel fraction (degree of crosslinking) are studied. The recipe and operation conditions are optimized as follows: a mass ratio of 3:1 for styrene (St)/dodecyl methacrylate or St/butyl acrylate, 0.5 wt % BPO, and 80°C for 7–8 h. The effect of the physical crosslinker (PB) concentration is complex. The oil absorbency increases with increasing PB at lower EGDMA concentrations. However, under this same condition, particles cannot be formed if the PB concentration is higher than a certain value. By contrast, there is an optimum PB concentration when the EGDMA concentration is higher. The oil absorption speed is also investigated. The presence of PB can speed up absorption. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3309–3314, 2003     

2‐Hydroxyethylmethacrylate carrying uniform porous particles: preparation and electron microscopy

Uniform macroporous particles carrying hydroxyl groups have been obtained in the size range 3–11.5 µm by seeded polymerization. For this purpose, uniform polystyrene particles in the size range 1.9–6.2 µm were used as seeds. The seed particles were successively swollen by dibutyl phthalate (DBP) and a monomer mixture comprising styrene, 2‐hydroxyethylmethacrylate (HEMA) and a crosslinker. Two different crosslinkers, divinylbenzene (DVB) and ethylene glycol dimethacrylate (EGDMA), were tested. Size distribution properties together with bulk and surface structures of the particles have been characterized by both scanning and transmission electron microscopy. While EGDMA provides uniform particles with a non‐porous surface, DVB produces uniform particles having a highly porous surface and interior. The comparison of FTIR and FTIR‐DRS spectra shows that the HEMA concentration is higher on the particle surface than within the particle interior. Seed latex size and monomer/seed latex ratios are identified as the most important variables affecting the final particles. Different seed latexes have been tried; the result is that highly macroporous particles with a sponge‐like pore structure both on the surface and in the particle interior have been obtained by use of the seed latex with the largest particles and the lowest molecular weight. An increase in the HEMA feed concentration leads to final particles with a non‐porous surface and a crater‐like porosity in the particle interior. The average pore size significantly decreases with increasing DBP/seed latex and monomer/seed latex ratios. © 2001 Society of Chemical Industry     

Synthesis and characterization of pH‐sensitive crosslinked (NIPA‐co‐AAC) nanohydrogels copolymer

A thermoresponsive polymeric nanohydrogels has been synthesized by inverse microemulsion polymerization of N‐isopropylacrylamide (NIPA) and acrylic acid (AAc) using Aerosol (AOT) as a surfactant, ethylene glycol dimethacrylate (EGDMA) as a crosslinker, and 2,2′‐azobisisobutyronitrile (AIBN) as initiator. The effect of concentration of AIBN, EGDMA, and NIPA/AAc weight ratio was investigated. The lower critical solution temperature (LCST) of poly (NIPA‐co‐AAC) can be manipulated to be 40°C and 45°C which was correlated to amount of AAc that was copolymerized with NIPA. FTIR, 1H NMR, TEM, and DSC characterized the nanohydrogels. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Swelling and mechanical properties of crosslinked hydrogels containing N-vinylpyrrolidone

Copolymers of 2-hydroxyethyl methacrylate/N-vinyl-2-pyrrolidone (HEMA/NVP) and methyl methacrylate (MMA)/NVP were prepared in the presence of varying amounts of ethylene glycol dimethacrylate (EGDMA) and methylene diacrylamide (MDA) as crosslinkers by photopolymerisation. The resultant solid polymers were swollen to equilibrium in water at 293 K to produce hydrogels. These hydrogels were characterised by soluble fraction and equilibrium water content. The gels were also characterised by compression—strain measurements, which enabled the calculation of Young's modulus and effective crosslink density. The differences in these properties of HEMA/NVP and MMA/NVP polymer series and the effects of MDA versus EGDMA as a crosslinker were explained in terms of compositional drift of polymerisation, heterogeneous crosslinking and hydrophilicity/hydrophobicity of the components involved. In comparison with EGDMA, MDA was found to be more effective in reducing the soluble fraction of the polymers studied and to produce less rigid networks when swollen.     

Effect of crosslinkers on size and temperature sensitivity of poly(N-isopropylacrylamide) microgels

In this work, we study the effect of crosslinkers on the size and swelling properties of temperature sensitive N-isopropylacrylamide (NIPAAm) microgels produced by dispersion polymerization. The crosslinkers studied were N,N′-methylenebisacrylamide (MBA), ethylene glycol dimethacrylate (EGDMA) an 3,9-divinyl-2,4,8,10-tetra-oxaspiro[5.5] undecane (DVA). The type of crosslinker had a major impact on the size and swelling behavior, although the proportion of crosslinker used in each case was low (maximum 5 mol%). The effect can be related to the hydrophilic/hydrophobic characteristics of the crosslinkers. DVA produces smaller hydrogels with reduced swelling ratio, MBA produces bigger microgels with higher swelling ratio, while EGDMA results in an intermediate behavior. With increasing amount of crosslinker used in the synthesis, the extent of the swelling ratio decreases for DVA and EGDMA crosslinked microgels, while increases for MBA crosslinked microgels. There is also a slight effect on the critical transition temperature (T _c) of the microgels from 30 °C (DVA) to 34 °C (MBA) as observed in copolymers of NIPAAm with hydrophilic or hydrophobic comonomers.     

Effect of tricalcium phosphate,hydroxyethyl methacrylate,and ethylene glycol dimethacrylate on the mechanical properties of acrylic bone cement

The effects of the addition of tricalcium phosphate (TCP), hydroxyethyl methacrylate (HEMA), and ethylene glycol dimethacrylate (EGDMA) on the properties of standard surgical Simplex-P radiopaque bone cement have been investigated. The fracture surface after tensile test was studied by scanning electron microscopy. The influence of these components on the temperature rise during polymerization was investigated. It was found that the tensile strength, the bending strength, and the compressive strength decreased with increasing TCP content, whereas the inverse was observed for the Young's modulus. The tensile strength slightly increased with increasing HEMA content and then it levelled off when the HEMA content was higher than 15 wt.-%. It seemed that there were maximum tensile, bending and compressive strengths when 2 wt.-% EGDMA (in HEMA) was added. Polymerization occurred more rapidly when HEMA and EGDMA were added, whereas the inverse result was found with TCP.     

Influence of the base and diluent methacrylate monomers on the polymerization stress and its determinants

The aim of this study was to evaluate the effect of the association between bisphenol‐A diglycidyl dimethacrylate (BisGMA) or its ethoxylated version (BisEMA) with diluents derived from the ethylene glycol dimethacrylate (EGDMA), with increasing number of ethylene glycol units (1: EGDMA, 2: DEGDMA, 3: TEGDMA, or 4: TETGDMA), or trimethylol propane trimethacrylate (TMPTMA) or 1,10‐decanediol dimethacrylate (D₃MA) on polymerization stress, volumetric shrinkage, degree of conversion, maximum rate of polymerization (Rp_max), and elastic modulus of experimental composites. BisGMA containing formulations presented lower shrinkage and stress but higher modulus and Rp_max than those containing BisEMA. TMPTMA presented the lowest stress among all diluents, as a result of lower conversion. EGDMA, DEGDMA, TEGDMA, and TETGDMA presented similar polymerization stress which was higher than the stress presented by D₃MA and TMPTMA. D₃MA presented similar conversion when copolymerized with both base monomers. The other diluents presented higher conversion when associated with BisEMA. EGDMA showed similar shrinkage compared with DEGDMA and higher than the other diluents. The lower conversion achieved by TMPTMA did not jeopardize its elastic modulus, similar to the other diluents. Despite the similar conversion presented by D₃MA in comparison with EGDMA and DEGDMA, its lower elastic modulus may limit its use. Rather than proposing new materials, this study provides a systematic evaluation of off the shelf monomers and their effects on stress development, as highlighted by the analysis of conversion, shrinkage and modulus, to aid the optimization of commercially available materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

苯乙烯/丙烯酸丁酯交联体系乳液聚合动力学研究

以十二烷基苯磺酸钠(SDBS)为乳化剂,过硫酸钾(KPS)引发苯乙烯/丙烯酸丁酯(St/BA)乳液共聚,加入二甲基丙烯酸乙二醇酯(EGDMA)、聚丁二烯生胶(PB)作为交联剂,研究了聚合温度、引发剂浓度、乳化剂浓度、单体配比对聚合速率的影响。实验结果表明,共聚体系的表观活化能为70.67kJ/mol,聚合初始速率与引发剂浓度的0.43次方、乳化剂浓度的0.56次方和单体BA的0.49次方成正比。     

Additive modification of the polymerization and properties of an acrylic bone cement

A commercial surgical bone cement has been modified by adding tricalcium phosphate (TCP), hydroxyethyl methacrylate (HEMA), and ethylene glycol dimethacrylate (EGDMA). The effects of the addition of TCP, HEMA, and EGDMA on the vinyl polymerization kinetics and thermal stability of the bone cement have been evaluated. The reaction rate constants (k) were determined from a kinetic analysis. The separate and combined effects of TCP, HEMA, and EGDMA contents on the rate and the heat of polymerization can be explained by the frequency factor and the activation energy. The decomposition temperture of the modified acrylic bone cement was studied by thermogravimetry. The decomposition temperature increased with TCP content, whereas HEMA and EGDMA had little effect on the decomposition temperature.     

Preparation and characterization of 2‐hydroxyethyl methacrylate‐based porous copolymeric particles

2‐Hydroxyethyl methacrylate was copolymerized with three different comonomers, methyl methacrylate (MMA), styrene (St), and N‐vinyl‐2‐pyrrolidone (NVP), respectively, to prepare porous particles crosslinked using ethylene glycol dimethacrylate (EGDMA) in the presence of an organic solvent, 1‐octanol (porogen), by means of suspension copolymerization in an aqueous phase initiated by 2,2‐azobisisobutyronitrile. Nano‐pores were observed in the particles. The pore size and the swelling properties of these particles can be controlled by changing comonomers or adjusting the crosslinker or porogen concentration. A lower crosslinker or porogen concentration favors generating smaller pores, whereas a higher concentration of a hydrophilic comonomer, higher concentration of crosslinker, and higher porogen volume ratio promote the generation of larger pores. In addition, the effects of the porous characteristics on the swelling properties were explored. The swelling capacity of the porous particles is reduced with the increase in the crosslinker concentration; however, there is a critical porogen volume ratio, in which the maximal swelling capacity is reached. Higher porosity in the particles and higher amount of hydrophilic comonomer favor a higher swelling capacity of the particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Observation for mechanical property variations of single polymer particles

Monodisperse polymer particles were prepared via conventional microsuspension polymerization or one‐step seeded polymerization, using 1,6‐hexanedioldiacrylate or its mixture with ethylene glycol dimethacrylate (EGDMA) as crosslinking monomer and poly(methyl methacrylate) synthesized by soap‐free polymerization as seed particles. For the study, the effects of the ratio of the absorbed monomer or monomer mixture to the seed polymer particles (swelling ratio), the ratio of EGDMA in absorbed monomer mixture, the dosage of initiator, polymer particle structure, and the electroless Ni plating on the mechanical properties of polymer particles, such as recovery rate, K‐values, breaking strength, and breaking displacement were investigated using micro compression test. It was observed that monomer swelling ratio influenced only on breaking strength, whereas EGDMA ratio in monomer mixture, dosage of initiator, polymer structure and electroless Ni plating did on both K‐values and breaking strength. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

The development of chemically modified P84 Co-polyimide membranes as supported liquid membrane matrix for Cu(II) removal with prolonged stability

We have demonstrated, for the first time, P84 co-polyimide with novel chemical cross-linking modification can be effectively used as the polymeric microporous matrix for supported liquid membrane (SLM) applications. Both asymmetric and symmetric flat membranes with high tortuosity were fabricated via the phase inversion method. It is found that the symmetric membrane outperforms the asymmetric one because the former may provide (1) balanced forces exerted at two aqueous/membrane interfaces and (2) the formation of more stable stagnant layers than the latter. However, the performance of both unmodified asymmetric and symmetric flat membranes deteriorates severely after use for 20-30 h. A novel chemical modification agent, p-xylenediamine/water, was discovered and shows effectiveness to improve P84 membrane stability for SLM. The improved SLM stability is attributed to the reduced pore size and the enhanced hydrophobicity on the membrane surfaces. The newly developed chemically modified SLM has a similar lifetime compared with other SLM systems using commercial PTFE as the support matrix.     

Delaying the onset of macrogelation for the synthesis of branched and star-like polymers via conventional free-radical polymerisation: Binary solvent effects and incorporation of surfmers

It is known that the preferential solvation and conformation of a polymer in a solvent mixture are functions of the polymer's molecular weight and the solvent qualities. This paper demonstrates that these relationships can be exploited to delay the onset of macrogelation for branched poly(methyl methacrylate/ethylene glycol dimethacrylate) (p(MMA/EGDMA)) polymers and star-like poly(methyl acrylate/ethylene glycol dimethacrylate) (p(MA/EGDMA)) polymers synthesised via conventional free-radical polymerisation (CFRP) in a binary solvent mixture (consisting of a good solvent and a precipitant for the polymer). The gelation limits of the MMA/EGDMA and MA/EGDMA polymerisations in a methyl ethyl ketone (MEK)/heptane binary solvent mixture can be extended to regions of higher monomer concentration with increases in polymer yield between 13 and 50 ± 5 w/w% for the p(MMA/EGDMA) system and between 8 and 19 ± 6 w/w% for the p(MA/EGDMA) system across the gelation boundary. Thus, a facile method of increasing the concentration of batch reaction mixtures by the simple addition of small amounts of precipitant into the reaction solutions is presented. Furthermore, the gelation limits of both polymerisation systems in the binary solvent mixtures were further extended with increases in polymer yield between 11 and 17 ± 4%w/w for the p(MMA/ODA/EGDMA) system and between 8 and 20 ± 5%w/w for the p(MA/VS/EGDMA) system by the respective incorporation of octadecyl acrylate (ODA) and vinyl stearate (VS) surfmers into the polymers, demonstrating the application of steric hinderance to shield the propagating polymers from excessive cross-linking reactions.     

Characteristics of water-absorbent polymer emulsions

Water-in-Oil (W/O) and Oil-in-Water (O/W) type water absorbent polymer emulsions were studied using two different polymerization methods. W/O type water absorbent polymer emulsions were prepared by the inverse emulsion polymerization of ammonium acrylate (AA), the quaternized salt of dimethyl-aminoethyl methacrylate (DMQ) and acrylamide (AM) with N,N-methylene-bisacrylamide (MBA) as a crosslinker. A pH sensitive water absorbent polymer emulsion was prepared by the conventional emulsion polymerization of diethyl-aminoethyl methacrylate (DEAEMA) with ethylene glycol dimethacrylate (EGDMA) as a crosslinker. It was confirmed that the water absorption capacity of crosslinked polymers in inverse emulsion was controlled by crosslink density and dissociative charge density, and the crosslinked polyDEAEMA particles had a phase transition property of swelling and shrinking with pH. The dispersions of these water swollen crosslinked polymer particles exhibited an increase in viscosity and thixotropic fluidity.