Polymerization of adsorbed monolayers. III. Preliminary structure studies in dilute solution of the insertion polymers

Insertion poly(methyl acrylate) and poly(methyl methacrylate) were prepared from monomers adsorbed in monolayers on the surface of montmorillonite clay, both in the presence and in the absence of bifunctional crosslinkers (ethylene glycol dimethacrylate and tetramethylene glycol dimethacrylate). The insertion poly(methyl acrylate) and the crosslinked insertion poly(methyl methacrylate) and dilute-solution properties quite different from conventional polymers of these monomers, the differences including high light-scattering molecular weights combined with low viscosities, low values of the second virial coefficient, unusually large variations of the Huggins' constant k′ with the time-temperature history of the solutions, and low sedimentation velocities. These properties suggest that the insertion polymers have compact structures and are consistent with the postulate of sheetlike macromolecules. The dilute-solution properties of insertion poly(methyl methacrylate) made without crosslinker, unlike those of similarly prepared poly(methyl acrylate), were similar to those of conventional poly(methyl methacrylate). This difference in behavior is attributed to the different tendencies of the two monomers to undergo branching or crosslinking during radical polymerization.     

Polyhydroxy and polyethyleneglycol (meth)acrylate polymers: physical properties and general studies for their use as electrophoresis matrices.

A new series of materials have been tested for their suitability as electrophoresis matrices. The mechanical and optical properties of gels composed of polyethyleneglycol (meth)acrylate esters or polyhydroxy (meth)acrylate esters in water and in various concentrations of organic solvents are described. Several crosslinkers including polyethyleneglycol and polyhydroxy di(meth)acrylates, piperazine diacrylate, and bisacrylamide were used in these studies. Electrophoretic migration and separation of a series of protein standards through polyethyleneglycol methacrylate (PEGM) 200, PEGM 400, and glyceryl methacrylate is demonstrated. Further, copolymerization of all of the monomers with acrylamide was performed and the distribution of monomer incorporation into the polymer network calculated. All monomers and copolymers that were examined by IR spectroscopy showed greater than 99% polymerization. These results justify their further study for biomolecule separations.     

Poly(ethylene glycol)‐based amphiphilic model conetworks: Synthesis by RAFT polymerization and characterization

Poly(ethylene glycol) (PEG)‐containing quasi‐model amphiphilic polymer conetworks (APCNs) were prepared by reversible addition fragmentation chain transfer (RAFT) polymerization using α,ω‐bis(2‐cyanoprop‐2‐yl dithiobenzoate)‐PEG as a bifunctional RAFT macrochain transfer agent (macro‐CTA) and stepwise additions of a hydrophobic monomer and a crosslinker (crosslinker: macro‐CTA = 10:1, reaction time 24 h). Three different types of monomers, methyl methacrylate (MMA), n‐butyl acrylate and styrene, were employed as the hydrophobic monomers, whereas ethylene glycol dimethacrylate, ethylene glycol diacrylate and 1,4‐divinylbenzene served as the respective crosslinkers. PEG homopolymer hydrophilic quasi‐model networks were also prepared by RAFT‐polymerizing the three crosslinkers directly onto the two active ends of the PEG‐based macro‐CTA. From the three ABA triblock copolymers prepared, the MMA‐containing one was obtained at the highest polymerization yields. The crosslinking yields of the three ABA triblock copolymers with the corresponding crosslinkers were higher than those of the PEG‐based macro‐CTA with the same crosslinkers. The degrees of swelling (DSs) of all conetworks were measured in water and in tetrahydrofuran (THF). The DSs of the APCNs in THF were higher than those in water, whereas the reverse was true for the DSs of the hydrophilic homopolymer networks. Finally, the aqueous DSs of the APCNs were lower than those of the corresponding hydrophilic homopolymer networks. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7556–7565, 2008     

Alteration of bacterial nanocellulose structure by in situ modification using polyethylene glycol and carbohydrate additives

Bacterial nanocellulose (BC) is characterized by an exciting interconnection of the important and well-known cellulose properties with the outstanding features of nano-scale materials. As a remarkable benefit of BC the property-controlling fiber network and pore system formed by self-assembly of the cellulose molecules can be modified in situ using additives during biosynthesis. The addition of polyethylene glycol (PEG) 4000 causes a pore size decrease. In presence of β-cyclodextrin or PEG 400 remarkably increased pores can be achieved. Surprisingly, these co-substrates act as removable auxiliaries not incorporated in the BC samples. In contrast, carboxymethyl cellulose and methyl cellulose as additives lead to structural modified composite materials. Using cationic starch (2-hydroxy-3-trimethylammoniumpropyl starch chloride, TMAP starch) double-network BC composites by incorporation of the starch derivative in the BC prepolymer were obtained.     

不同交联剂对甲基丙烯酸-β-羟乙酯/E-51双甲基丙烯酸酯聚合物水凝胶性能的影响

以水溶性单体甲基丙烯酸-β-羟乙酯(HEMA)与大分子交联剂E-51双甲基丙烯酸酯(E-51-DMA)(质量比HEMA/E-51-DMA=90/10)为主要原料,分别引入了5种小分子交联剂:N,N′-亚甲基双丙烯酰胺(MBA)、二乙烯基苯(DVB)、双甲基丙烯酸乙二醇酯(EDMA)、1,1,1-三(丙烯酰氧甲基)丙烷(TAP)和2,2,2-三(丙烯酰氧甲基)乙醇(TAE),采用本体聚合方法合成了5个系列的聚合物水凝胶.研究了小分子交联剂的类型及用量对水凝胶溶胀性能、杨氏模量以及有效交联密度ve和聚合物-水相互作用参数χ的影响,并比较了不同交联剂的交联效率.结果表明,随着小分子交联剂用量的增大,水凝胶平衡含水量EWC逐渐降低,聚合物体积分数2逐渐增大,反映聚合物网络结构的有效交联密度ve以及热力学参数聚合物-水相互作用参数χ值也随之增大.通过理论交联密度和有效交联密度的线性拟合,得到所选用的5种小分子交联剂在E-51-DMA10/HEMA90水凝胶体系中的交联效率,其顺序为DVB>EDMA>TAE>MBA≈TAP.     

Novel membranes made from a semi-interpenetrating polymer network for ethanol–ETBE separation by pervaporation

The design of high-performance pervaporation membranes for the selective removal of ethanol from ethyl t-butyl ether (ETBE) was performed by using semi-interpenetrating polymer network (s-IPN) materials. The chosen linear polymer in the s-IPN was a cellulose ester, and the network was formed by photopolymerization of a dimethacrylate, or a dimethacrylate and one or two co-monomers. Membranes with good mechanical properties and moderate to good selectivity were obtained. Large permeability increases without loss in selectivity were observed with s-IPN films formed by cellulose propionate or cellulose butyrate interpenetrated by a network of poly(ethyleneglycol dimethacrylate). The use of dimethacrylate with longer spacers of the poly(ethoxy) type in these materials further increased the permeability. The permeation flux of cellulose acetate-based membranes is improved only when a methacrylate with poly(ethoxy) side chains is incorporated in the network by copolymerization with the poly(ethoxy)-type dimethacrylate. When the poly(ethyleneglycol dimethacrylate) in cellulose butyrate-based s-IPN films increases, the selectivity remains constant, while the film permeability goes through a maximum. The results are interpreted on the basis of a “plasticization” effect exerted on the linear polymer by interpenetrated networks composed of methacrylates with poly(ethoxy) chains. The resulting improved segment mobility favors the permeability at low network contents. The stability of s-IPN membranes in hot liquid mixtures was explained by extended entanglements of the linear polymer with the branches of the network meshes. © 1997 John Wiley & Sons, Ltd.     

Semi‐micro reversed‐phase liquid chromatography for the separation of alkyl benzenes and proteins exploiting methacrylate‐ and polystyrene‐based monolithic columns

Monolithic columns were synthesized inside 1.02 mm internal diameter fused‐silica lined stainless‐steel tubing. Styrene and butyl, hexyl, lauryl, and glycidyl methacrylates were the functional monomers. Ethylene glycol dimethacrylate and divinylbenzene were the crosslinkers. The glycidyl methacrylate polymer was modified with gold nanoparticles and dodecanethiol (C₁₂). The separation of alkylbenzenes was investigated by isocratic elution in 60:40 v/v acetonitrile/water. The columns based on polystyrene‐co‐divinylbenzene and poly(glycidyl methacrylate)‐co‐ethylene glycol dimethacrylate modified with dodecanethiol did not provide any separation of alkyl benzenes. The poly(hexyl methacrylate)‐co‐ethylene glycol dimethacrylate and poly(lauryl methacrylate)‐co‐ethylene glycol dimethacrylate columns separated the alkyl benzenes with plate heights between 30 and 60 μm (50 μL min^?1 and 60°C). Similar efficiency was achieved in the poly(butyl methacrylate)‐co‐ethylene glycol dimethacrylate column, but only at 10 μL min^?1 (0.22 mm s^?1). Backpressures varied from 0.38 MPa in the hexyl methacrylate to 13.4 MPa in lauryl methacrylate columns (50 μL min^?1 and 60°C). Separation of proteins was achieved in all columns with different efficiencies. At 100 μL min^?1 and 60°C, the lauryl methacrylate columns provided the best separation, but their low permeability prevented high flow rates. Flow rates up to 500 μL min^?1 were possible in the styrene, butyl and hexyl methacrylate columns.     

乳液聚合法制备聚合物与十二醇复合乳胶粒

通过乳液聚合法, 以苯乙烯、丙烯酸丁酯为主要单体, 以甲基丙烯酸为功能性单体, 以二乙烯基苯或二甲基丙烯酸乙二醇酯为交联剂, 制备了包覆有十二醇的聚合物复合颗粒. 通过动态光散射粒径仪和透射电镜观测乳胶粒粒径和形态, 气相色谱法测试了十二醇的包覆率, 并探讨了聚合过程中十二醇包覆率的变化情况. 结果表明十二醇的包覆率和十二醇与单体的质量比及单体转化率显著相关, 并且在聚合过程中包覆率存在先升后降的趋势. 实验发现十二醇包覆率的先升后降是由聚合物和十二醇的相容性不好引起的.     

甲基丙烯酸羟乙酯改性水性聚氨酯乳液的制备及性能

采用种子溶胀乳液聚合法,以水性聚氨酯为种子,甲基丙烯酸羟乙酯、甲基丙烯酸甲酯和丙烯酸丁酯为单体制备水性聚氨酯丙烯酸酯复合乳液,考察了甲基丙烯酸羟乙酯含量对复合乳液的T型剥离、胶膜的硬度、耐水性和力学性能的影响。结果表明,随着甲基丙烯酸羟乙酯含量的增加,复合乳液的T型剥离强度、胶膜的硬度和拉伸强度增大,胶膜的耐水性先增大后减小,断裂伸长率有所降低,适宜的甲基丙烯酸羟乙酯用量为3%。     

Modified suspension‐PVC particles as absorbents of ortho‐dichlorobenzene from water

Modified porous PVC particles are studied as absorbents of o‐dichlorobenzene (DCB), from water. The modified particles were produced by an in‐situ stabilizer‐free polymerization/crosslinking of a monomer/crosslinker/peroxide solution absorbed within commercial porous suspension‐type PVC particles. The modifying monomers used include styrene with divinyl benzene (DVB) as a crosslinking comonomer, methyl methacrylate (MMA), butyl acrylate (BA), or ethylhexyl acrylate (EHA) with ethylene glycol dimethacrylate (EGDMA) as a crosslinking comonomer. The effect of the nature of the monomers, morphology, porosity, surface area and composition of the modified PVC particles on DCB absorption was studied. Batch experiments (absorption rate and isotherms) were used to screen the PVC absorbents on the basis of absorption rate and absorption capacity. Continuous absorption column experiments were conducted to study the parameters characterizing the absorption process. Both the unmodified and modified PVC particles absorb DCB from water. The PBA and PEHA‐modified PVC particles approach equilibrium capacity faster and have greater absorption capacity than neat PVC, PS‐modified PVC and PMMA‐modified PVC particles. The absorption characteristics are influenced by the modifying polymer's T_g. The rubbery nature of PBA and PEHA yields better absorption in spite of the significantly lower surface area and porosity obtained in the modified PVC particles. Thus, indicating that fast adsorption followed by bulk absorption of DCB is taking place. A clear influence of the crosslinking effect was not established. The continuous absorption experiments were found more efficient than the batch absorption experiments. Copyright © 2003 John Wiley & Sons, Ltd.     

Synthesis and characterization of novel fluoride‐releasing monomers. II. Dimethacrylates containing bis(aminodiacetic acid) and their ternary zirconium fluoride complexes

Novel dimethacrylate monomers containing bis(aminodiacetic acid) chelating ligands with or without additional hydroxyl groups were synthesized, starting from 2,2‐bis(4‐hydroxy‐3‐methylphenyl)propane. The structures of the monomers were characterized by electrospray mass spectrometry (ESMS), ¹H NMR, and ¹³C NMR. The structures and relative stability of fluoride‐releasing monomers containing one or more ternary zirconium fluoride complex moieties were studied by ESMS. The most stable ternary zirconium fluoride complex was in the form of [LZrF]^?, where H₄L is the monomer containing bis(aminodiacetic acid) without additional hydroxyl groups. The synthesized monomer was photopolymerized with camphorquinone and 1‐phenyl‐1,2‐propane‐dione as initiators and N,N‐dimethylaminoethyl methacrylate as the accelerator. The fluoride release, fluoride recharge, compressive strength, and flexure strength were tested on the experimental dental composite containing 13.7 wt % synthesized monomer and three commercial flowable dental composites. The results showed that the experimental composite has significantly higher fluoride release and recharge capabilities than the commercial flowable composites. The compressive strength was comparable to that of the commercial materials. The water sorption and solubility met the requirement of the ISO Specification 4049. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3153–3166, 2005     

Water uptake and dye sorption studies of chemically crosslinked highly swollen novel ternary acrylamide‐based hydrogels including citraconic acid and sodium acrylate

Highly swollen hydrogels made by the polymerization of acrylamide (AAm) with some anionic monomers such as citraconic acid (CITA) and sodium acrylate (SA) were investigated as a function of composition to find materials with swelling and dye sorption properties. Highly swollen AAm/CITA/SA or AAm/SA/CITA hydrogels were prepared by free radical solution polymerization in aqueous solutions of AAm with CITA and SA as co‐monomers and two multifunctional crosslinkers such as ethylene glycol dimethacrylate (EGDMA) and 1,4‐butanediol dimethacrylate (BDMA). Swelling experiments were performed in water at 25°C, gravimetrically. Chemically crosslinked AAm/CITA/SA or AAm/SA/CITA hydrogels were used in experiments on sorption of water‐soluble monovalent cationic dye such as “Nil blue” (Basic Blue 12; BB 12). Equilibrium percentage swelling values of AAm/CITA/SA or AAm/SA/CITA hydrogels were calculated in the range of 1797–22,098%. Some swelling kinetic parameters were found. Diffusion behavior of water was investigated. Water diffusion into the hydrogels was found to be non‐Fickian in character. For sorption of cationic dye, BB 12 into the hydrogels was studied by batch sorption technique at 25°C. AAm/CITA/SA or AAm/SA/CITA hydrogels in the dye solutions showed coloration, whereas AAm hydrogel did not show sorption of any dye from the solution. The sorption capacity of AAm/CITA/SA or AAm/SA/CITA hydrogels was investigated. At the end of the experiments, 21.70–78.91% BB 12 adsorptions were determined. Copyright © 2007 John Wiley & Sons, Ltd.     

半互穿聚合物网络BVV的制备及其性能研究

以丙烯酸丁酯(BA)和醋酸乙烯酯(VAc)为单体,对VAc与乙烯的共聚乳液(VAE)进行改性,通过乳液聚合制备了半互穿聚合物网络BVV.考察了乳化剂、交联剂、引发剂以及反应时间等条件对转化率及BVV稳定性的影响.BVV的剥离力度及其乳胶膜的吸水率的测定结果证明BVV耐水性及粘接强度较VAE明显增强.光学显微镜照片显示BVV的互穿结构已经形成.     

Controlling the water content of never dried and reswollen bacterial cellulose by the addition of water-soluble polymers to the culture medium

For the modification of medically useful biomaterials from bacterially synthesized cellulose, fleeces of Acetobacter xylinum have been produced in the presence of 0.5, 1.0, and 2.0% (m/v) carboxymethylcellulose (CMC), methylcellulose (MC), and poly(vinyl alcohol) (PVA), respectively, in the Hestrin-Schramm culture medium. The incorporation of the water-soluble polymers into cellulose and their influence on the structure, crystal modifications, and material properties are described. With IR and solid-state ¹³C NMR spectroscopy of the fleeces, the presence of the cellulose ethers and an increase in the amorphous parts of the cellulose modifications (NMR results) have been detected. The incorporation is represented by a higher product yield, too. As demonstrated by scanning electron microscopy, a porelike cellulose network structure forms in the presence of CMC and MC. This modified structure increases the water retention ability (expressed as the water content), the ion absorption capacity, and the remaining nitrogen-containing residues from the culture medium or bacteria cells. The water content of bacterial cellulose (BC) in the never dried state and the freeze-dried, reswollen state can be controlled by the CMC concentration in the culture solution. The freeze-dried, reswollen BC-CMC (2.0%) contains 96% water after centrifugation, whereas standard BC has only 73%. About 98% water is included in a BC-MC composite in the wet state, and about 93% is included in the reswollen state synthesized in the presence of 0.5, 1.0, or 2.0% MC. These biomaterial composites can be stored in the dried state and reswollen before use, reaching a higher water absorption than pure, never dried BC. The copper ion capacity of BC-CMC composites increases proportionally with the added amount of CMC. BC-CMC (0.5%) can absorb 3 times more copper ions than original BC. In the case of 0.5 and 1.0% PVA additions to the culture solution, this polymer cannot be detected in the cellulose fleeces after they are washed. Nevertheless the presence of PVA in the culture medium effects a decreased product yield, a retention of nitrogen-containing residues in the material during purification, a reduced water absorption ability, and a slightly higher copper ion capacity in comparison with original BC. The water content of freeze-dried, reswollen BC-PVA (0.5%) is only 62%. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 463–470, 2004     

Cellulose acetate/poly(methyl methacrylate) interpenetrating networks: synthesis and estimation of thermal and mechanical properties

IPN-type composites consisting of cellulose acetate (CA) and poly(methyl methacrylate; PMMA) were successfully synthesized in film form. In this synthesis, a mercapto group (SH)-containing CA, CA-MA, was prepared in advance by esterification of CA with mercaptoacetic acid, and then intercomponent cross-linking between CA-MA and PMMA was attained by thiol–ene polymerization of methyl methacrylate (MMA) onto the CA-MA substrate. For comparison, polymer synthesis was also attempted to produce a semi-IPN type of composites comprising CA and cross-linked PMMA, via copolymerization of MMA and ethylene glycol dimethacrylate as cross-linker in a homogeneous system containing CA solute. Thermal and mechanical properties of thus obtained polymer composites were investigated by differential scanning calorimetry, dynamic mechanical analysis, and a tensile test, in correlation with the mixing state of the essentially immiscible cellulosic and methacrylate polymer components. It was shown that the specific IPN technique using thiol–ene reactions usually resulted in a much better compatibility-enhanced polymer composite, which exhibited a higher tensile strength and even an outstanding ductility without parallel in any film sample of CA, PMMA, and their physical blends.     

Synthesis and characterization of novel aliphatic amine-containing dimethacrylate cross-linkers and their use in UV-curable resin systems

Two novel aliphatic amine-containing dimethacrylate monomers were synthesized from the ringopening reaction of hexamethylene diamine and ethylenediamine with glycidyl methacrylate. The UV-curable and heat-curable formulations were prepared with amine-containing dimethacrylate and active diluents. The curing process was controlled by Fourier transform infrared analysis. The mechanical, physical, and thermal characterizations of the UV-cured films and the UV-heat-cured films were investigated. Thermo-gravimetric analysis of the cured films revealed that the thermo-oxidative stability of the UV-heat-cured films was higher than that of the UV-cured samples. An increase in the cross-linker content caused an increase both in tensile strength and in the elongation values of the UV-heat-cured films. It was also found that the water absorption capacities and gel content of the UV-heat-cured dimethacrylated films depended on the amount of the active diluents.     

Effects of monomer structure on the morphology of polymer networks and the electro-optical properties of polymer-dispersed liquid crystal films

Polymer-dispersed liquid crystal (PDLC) films were prepared by photochemical polymerisation with a series of (meth)acrylate monomers. The effects of monomer structure on the morphology of polymer networks in the PDLC films were studied. The acrylate monomers without sidegroup chain formed uniform polymer networks. The methacrylate monomers with methyl as their sidegroup chains formed lace-like networks. The size of the LC droplets increased with increasing the length of the flexible chain of both methacrylate and acrylate monomers. Meanwhile, the effects of the morphology of the polymer network on the electro-optical properties of PDLC films were also investigated.     

Effect of crystallinity on radiation-induced graft copolymerization on cellulose

With vinyl monomers, viz., styrene, butyl methacrylate, dimethylaminoethyl methacrylate, and ethyl acrylate, it was noted that higher per cent grafting was obtained with “recrystallized” cellulose than with “amorphous” cellulose. The possibility of the production of a porous structure in cellulose as a result of γ-irradiation followed by the dissolution of the reactive regions is suggested. DTA and DTG data of irradiated cellulose triacetate (CTA) reveal lowering of the melting point on irradiation, indicating a decrease in crystallinity. Decrease in density of cellulose on irradiation by γ-rays also indicates loosening of the structure of cellulose. It is postulated that grafting occurs in those regions of cellulose which were crystalline before irradiation, as well as in less crystallinie regions.     

In situ formation of new crosslinking agents from acrylate derivatives and bisepoxides

The synthesis of several newly available diacrylate crosslinking agents derived from hydroxy functional acrylates and bisepoxides is described. These crosslinking agents are synthesized via the acid catalyzed addition of hydroxyl-containing acrylate monomers to bisepoxides derived from bisphenol-A and its hexafluoropropyl analog. These materials are generated in an excess of the acrylate monomer and the reaction mixtures are then converted directly to highly crosslinked materials. The alcohol functional monomers include hydroxyethyl methacrylate (HEMA) and the butyl and ethyl esters of (α-hydroxymethyl)acrylic acid. The latter are especially interesting for several reasons. First, they are readily available through the addition of the corresponding acrylate to formaldehyde. Second, these monomers react with the bisepoxides to give all-ether-linked connecting groups, in conrast to HEMA which yields a molecule with both ether and ester linkages between the two acrylate units. Third, the monomers are very different in solubility from HEMA and the polymers display very different chemical and physical properties. For example, while the crosslinked HEMA polymers are swellable in water, those of the (α-hydroxymethyl)acrylates are insoluble in water but swellable in organic solvents such as chloroform. All monomers, crosslinking agents, and crosslinked polymers were characterized by FT-IR, solution or solid state ¹³C-NMR spectroscopy, and thermal analysis.     

In situ modification of bacterial cellulose nanostructure by adding CMC during the growth of Gluconacetobacter xylinus

Many studies focus on bacterial cellulose (BC) functioning as multi-function bio-resource polymers, due to its fine fiber network, biocompatibility, high water holding capacity, and high mechanical strength. However, BC exhibits poor rehydration after drying due to its high crystallinity. This study added carboxymethylcellulose (CMC) to a BC producing culture medium, which interfered with the formation of BC structure in situ. This process created a modified BC called CBC, whose mechanical strength was found weaker than BC. Scanning electron microscope (SEM) images showed that the cellulose network in CBC became denser. X-ray diffraction and Fourier transform infrared spectroscopy (FTIR) analysis demonstrated that the addition of CMC reduced crystallinity. CBC also exhibited the highest rehydration ratio because of the lowest crystallinity at the 1.0% CMC addition level.