Dynamic mechanical properties and swelling of UV‐photopolymerized anionic hydrogels

The tensile dynamic mechanical properties and weight degree of swelling for anionic 2‐hydroxyethyl methacrylate‐co‐acrylic acid hydrogels were observed. Fabrication parameters examined were UV‐photopolymerization exposure time, UV‐photopolymerization intensity, and weight percentage crosslinker. The environmental conditions tested were electrolyte compositions of 0.5 and 0.05 M potassium hydroxide under applied frequencies of 0.1, 1, or 10 Hz. The overall maximum and minimum storage modulus was 1.83 ± 0.18 MPa and 68.5 ± 7.2 kPa, respectively, loss modulus was 432 ± 63 and 7.67 ± 3.22 kPa, respectively, and weight degree of swelling was 14.27 ± 1.27 and 1.95 ± 0.33, respectively. The morphology of fabricated hydrogels was examined using scanning electron microscopy showing a range of porous structures over the fabrication and environmental conditions examined, accounting for the variation in mechanical properties. The properties examined are of interest to researchers fabricating, designing, or modeling active hydrogel‐based microfluidic components. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Synthesis and some properties of acrylic and methacrylic derivatives of chlorophos and its analogs

Conclusions The reaction of chlorophos and its analogs with the acid chlorides of the acrylic, methacrylic and-fluoroacrylic acids gave some new unsaturated compounds that possess fungicidal action.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 883–886, April, 1973.     

Polymerization kinetics and volume relaxation behavior of photopolymerized multifunctional monomers producing highly crosslinked networks

Multifunctional monomers (trimethylol propane trimethacrylate, trimethylol propane triacrylate, pentaerythritol tetraacrylate, and dipentaerythritol monohydroxy pentaacrylate) were photopolymerized with 2,2-dimethoxy-2-phenylacetophenone as the photoinitiator to produce highly crosslinked networks. The volume shrinkage behavior and the reaction kinetics were studied under various reaction conditions. The volume shrinkage and maximum functional group conversion were dependent on the number of functional groups, type of functional group, and the curing conditions. The maximum functional group conversion was also dependent on the reaction temperature. All the polymerized systems exhibited a strong coupling between the volume relaxation and the reaction kinetics. The kinetic constants were also determined as a function of conversion, and the termination mechanism was found to be reaction diffusion dominated even at low conversions. The importance of these results on the prediction of the reaction behavior for multifunctional monomers producing highly crosslinked polymers is discussed. © 1994 John Wiley & Sons, Inc.     

Bis(fluoroalkyl)acrylic and methacrylic phosphate monomers, their polymers and some of their properties

Ten fluoromonomers of structure (R_FO)₂P(O)OCH₂CH₂OC(O)CRCH₂ were made in 30-64% yield by treating the chloridates (R_FO)₂P(O)Cl with HOCH₂CH₂OC(O)CRCH₂ in chloroform in the presence of triethylamine [R_F=CF₃CH₂, C₂F₅CH₂, C₃F₇CH₂, C₄F₉CH₂, C₄F₉CH₂CH₂ or C₆F₁₃CH₂CH₂; R  H or Me]. The chloromonomer (CCl₃CH₂O)₂P(O)OCH₂CH₂OC(O)CHCH₂ was obtained analogously in 29% yield. Polymerisation of the acrylate monomers, but not the methacrylate monomers, could be effected using α-azoisobutyronitrile as a radical initiator. Acrylic polymers having CF₃CH₂O, CCl₃CH₂O and C₆F₁₃CH₂CH₂O side-chains were obtained as translucent rubbers. Specimens of cotton fabric were treated with solutions of the polymers, and average water and oil repellency ratings measured. Fabric coated with the polymer with the C₆F₁₃CH₂CH₂O side-chain afforded protection from penetration of the test liquids. Treated fabrics were subjected to the limiting oxygen index (LOI) test according to BS EN ISO 4589-2 (1999): this test determines the point at which a material just burns in a volumetric flow of oxygen and nitrogen. The treated fabrics were more fire-resistant (LOI 22-29%) than the untreated fabric (LOI 18%). Fabric coated with the CCl₃CH₂O-based polymer can be considered fire-retardant (LOI 29%). The fluoromonomers were tested for anti-acetylcholinesterase activity and were found to be poor enzyme inhibitors; they are predicted to possess low acute toxicity.     

Dielectric and mechanical relaxation processes in methyl acrylate/tri-ethyleneglycol dimethacrylate copolymer networks

The dielectric properties of methylacrylate (MA)/tri-ethyleneglycol dimethacrylate (TrEGDMA) copolymers at different compositions, ranging from 0 to 100, were measured between −120 and 150 °C over the frequency range 0.1 Hz-1 MHz. In the given frequency range, three relaxation processes were detected by dielectric relaxation spectroscopy in homo poly-TrEGDMA and copolymers: the α process associated with the glass transition, and two secondary processes due to localized mobility. In PMA only one secondary process was observed besides the alpha relaxation process. The influence of copolymerization going from PMA, monofunctional softer component with a glass transition determined calorimetrically as 284 K, to poly-TrEGDMA, higher glass transition component, bifunctional, that also forms a dense network due to cross linking, reflects mainly in the alpha process that shifts to higher temperatures and becomes broader. The raise and broadening in the glass transition with TrEGDMA increase was also observed by dynamic mechanical thermal analysis and differential scanning calorimetry. The glass transition temperature of poly-TrEGDMA was not detected calorimetrically but a value of 429 K was estimated from the best fit of the Fox equation. In what concerns the secondary relaxation process detected in poly-TrEGDMA and copolymers at the lowest temperatures, it is related with local twisting motions of ethyleneglycol moieties, being designated as γ relaxation, while the process detected in the medium temperature range is associated with the rotation of the carboxylic groups as in poly(alkyl methacrylates), designated as β relaxation. This process is detected at much lower temperatures in homo PMA in the same temperature region than the above mentioned γ relaxation. The copolymerization influences mainly the α process while the γ process remains almost unaffected in copolymers relative to homo poly-TrEGDMA. The β process is largely determined by the presence o the tri-ethylene glycol dimethacrylate monomeric units even in copolymers with the lowest TrEGDMA content.     

Photopolymerization studies of alkyl and aryl ester derivatives of ethyl α-hydroxymethylacrylate

Several new benzoate ester derivatives of ethyl α-hydroxymethylacrylate were synthesized using phase transfer catalysis and found to display unexpectedly rapid photopolymerization; i.e., from 2 to 8 times faster than MMA. New derivatives described here include the 4-fluoro-, 4-trifluoromethyl-, 4-methyl-, 2-hydroxy-, 4-nitro-, 4-methoxy-, 4-cyano-, and 3,4,5-trimethoxybenzoate esters along with the parent benzoate ester. Relative reactivities of these monomers in photopolymerizations were compared with those of the nonaromatic formate, acetate, hexanoate, and stearate derivatives. Reactivities of the nonaromatic ester derivatives increased with the length of the side chain while for the more reactive aromatic esters, rates increased in the order 4-methyl-, 4-fluoro- and benzoate < 4-trifluoromethyl- and 2-hydroxy- < 4-cyano- < 4-methoxy- < 3,4,5-trimethoxybenzoate. T_gs of the benzoate polymers ranged from 125°C for the 4-fluoro to 163°C for the 4-cyanobenzoate while those of the alkyl ester derivatives ranged from 15 to 78°C. Number average molecular weights of photoinitiated polymers (ca 10,000–20,000) were lower than those found for bulk and solution polymers (20,000—708,000) consistent with higher radical concentrations from photoinitiation. These materials greatly expand the number of candidates available for rapid photocure in thin film and coating applications, especially because their physical properties are those of linear rather than highly crosslinked structures formed from multifunctional systems. © 1996 John Wiley & Sons, Inc.     

Correlation between mechanical adhesion and interfacial properties of starch/biodegradable polyester blends

Biopolymers are preferred ingredients for the manufacture of materials because they are based on abundantly available and renewable raw materials that have benign environmental problems associated with their production, fabrication, use, and disposal; however, the wide use of biopolymers in engineering applications has not been achieved, mainly because of the inferior quality of many biopolymer‐based products. To overcome this limitation, studies have been initiated on blends of biopolymers and biodegradable synthetic polymers. We used the contact angle of probe liquids to measure the surface energy of polystyrene, the biodegradable polyesters polycaprolactone, poly(hydroxybutyrate‐co‐hydroxyvalerate), polylactic acid, polybutylene adipate terephthalate, and adipic poly(hydroxy ester ether), and normal starch. The surface energies were used to estimate the starch/polymer interfacial energy and work of adhesion. The calculated starch/polyester work of adhesion showed mixed correlation with published starch/polyester mechanical properties, indicating that factors other than interfacial properties might be dominant in determining the mechanical properties of some starch/polyester blends. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 920–930, 2001     

Synthesis and properties of miscible epoxy/acrylic interpenetrating polymer networks

Three series of epoxy/acrylic interpenetrating polymer networks were prepared by the simultaneous polymerization of diglycidyl ether of bisphenol A, crosslinked with an aliphatic diamine, diglycidyl ether of bisphenol A dimethacrylate, bisphenol A dimethacrylate, and diethoxy bisphenol A dimethacrylate. Under the conditions provided it is believed that the two networks form simultaneously but independently. Differential scanning calorimetry and dielectric measurements indicate that these polymer networks are miscible because they exhibit a single, sharp glass transition temperature, the values of which, however, are lower than predicted by the law of mixture. This decrease may be due in part to the dilution of one network by the other and to the resulting breakage of intramolecular interactions. It is also due, in part or in whole, to the presence of solvent and/or monomer impurities that act as plasticizers.     

Fluorescent and photochemical properties of TbIII complexes with acrylic acid-based macromolecular ligands

The fluorescent and photochemical properties of Tb^III complexes with macromolecular ligands based on acrylic acid were studied. The photochemical behavior of the macromolecular Th^II complexes with acrylic acid-alkyl methacrylate copolymers differs considerably from those of Tb^III complexes with polyacrylic acid and of low-molecular-weight analogs; in the former case, the intensity of Tb³⁺ photoluminescence noticeably increases during photolysis rather than decreases. It was found that the increase in the length of the alkyl group in the alkyl methacrylate favors the enhancement of the luminescence during the photolysis. The higher efficiency of the enhancement of the Eu³⁺ fluorescence during the photolysis of similar complexes of Eu³⁺ compared to the complexers of Tb³⁺ is due to the nature of the electrodipole hypersensitive⁵D₀–⁷F₂ transition in Eu³⁺.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2007–2010, August, 1996.     

Aspects regarding the characteristics of some acrylic and methacrylic polyesters synthesized in a magnetic field

The effect of a continuous external magnetic field on the characteristics of some acrylic and methacrylic polyesters synthesized in the field has been examined. The studies have been seen to show the difference between the molecular weights, cohesive energy densities, behaviour of thermal degradation as well as IR spectra of the polymers obtained in the field in comparison with the polyesters synthesized by classic bulk polymerization.     

Morphological analysis of photocured polyurethane acrylate networks. Correlation with viscoelastic properties

In this paper, we investigate the final morphology of photocured polyurethane acrylates based on polypropylene oxide by means of Transmission Electron Microscopy (TEM), Small Angle X‐ray Scattering (SAXS), and dynamic mechanical measurements. Two interrelated structural features on two different size scales can occur in these systems. TEM analysis demonstrates the presence of inhomogeneities on the length scale of 10–200 manometers, mostly constituted by clusters of small hard units (diacrylated diisocyanate) connected by polyacrylate chains. The bimodal shape of the dynamic mechanical relaxation spectra corroborates this two‐phase structure. Besides, a suborganization of the reacted diisocyanate hard segments inside the polyurethane acrylate matrix is revealed by SAXS measurements, depending on the nature of the hydroxylacrylate used for the synthesis of the precursor. Finally, UV‐exposure time is found to induce modifications on the viscoelastic properties of the final network, even at high double‐bond conversion: this effect can be due to a postreaction and to an increase of the crosslinking density inside the hard segments domains. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 919–937, 1999     

Preparation and properties of 1-ethoxy-2,2,2-trifluoroethyl esters of acrylic and methacrylic acids and of their polymers

1-Ethoxy-2,2,2-trifluoroethyl esters of acrylic ( I ) and methacrylic ( II ) acids were synthesized from 1-ethoxy-2,2,2-trifluoroethanol and acryloyl- and methacryloylchloride, respectively, and their densities, mass, ¹H- and ¹³C-NMR spectra were measured and the rate constants of hydrolysis were determined. Poly( I ) and poly( II ) were prepared by radical homopolymerization; the rates of polymerization, specific volume contractions in polymerization, limiting viscosity numbers, average number degrees of polymerization, temperature dependences of the heat capacities both in glass and liquid state, glass transition temperatures, and the initial temperature of the spontaneous thermal decomposition of homopolymers were determined. The monomer reactivity ratios of the styrene (S) copolymerizations, S? I and S? II , and the Alfrey–Price copolymerization constants e and Q for I and II were calculated from the composition of copolymers of I and II with styrene.     

Dynamic mechanical properties of random ethylene/1-octene copolymers prepared by rapid cooling

The dynamic mechanical properties of a well-characterized series of homogeneous ethylene/1-octene copolymers with different random hexyl branch contents and prepared using different cooling conditions have been examined using dynamic mechanical analysis (DMA). It was confirmed that the relaxation behavior of copolymers varied continuously with the branch content: the magnitude of the β relaxation increased with branch content while the intensity of the α relaxation decreased with the branch content; both relaxation temperatures decreasing with increasing branch level in the copolymers. Copolymers prepared at different cooling conditions were further examined and strikingly continuous changes were found for the first time. The β relaxation was shown to correlate to the amorphous region, while the α₁ and α₂ relaxations can be clearly differentiated for some samples and are assumed to be associated with the interlamellar slip and intra-crystalline c-shear processes respectively. With increasing cooling rate, the relative intensity of α₁ relaxation to α₂ relaxation was found to decrease while the β relaxation did not change. The most informative data is determined from deconvolution of tan δ spectra. In higher crystallinity polymers the α₁ and α₂ relaxations are closely related in activation energy but have different temperature locations. For lower crystallinity systems, where the α₁ relaxation cannot be observed, the α₂ and β relaxations are closely linked, with activation energies approaching one another. These results show very clearly that, although the observed relaxation data can be separated through deconvolution into three separate peaks, the behaviors are closely linked. Presumably, this a clear reflection of the role of tie molecules in binding phases together and in influencing dynamic mechanical behavior. A clear change of behavior has also been observed in the β relaxation when a distinct amorphous phase exists outside of the spherulites, confirming the general belief that the crystalline phase influences the amorphous phase when it is confined within a spherulite. Again, this behavior is reflecting the role of tie molecules in binding together the nanocomposite structure of a spherulite.     

Correlations between structure and some mechanical properties of carbon fibres

Three types of carbon materials were studied by X-ray analysis in order to get correlations between structure and some mechanical properties. Both X-ray and mechanical measurements were done in various conditions.     

Correlation between magnetic properties and molecular structure of some metallo-mesogens

The behaviour of a large number of paramagnetic metallo-mesogenic molecules with Cu and VO in different mesophases in a magnetic field was investigated by EPR techniques and magnetic susceptibility measurements. The investigation of the angular dependence of the EPR spectra enabled conclusions to be reached concerning the molecular orientation in the external magnetic field. Temperature dependence magnetic susceptibility measurements were carried out in order to obtain information about the overall susceptibility anisotropy. The good agreement between experimental results and calculated data based on the known increment scheme is obvious. It is shown that the direction of orientation of the molecules in a magnetic field is predetermined by the sum of the anisotropy of the phenyl ring and the chelate core in the molecular structure.     

Photopolymerization kinetics of ionic liquid monomers derived from the neutralization reaction between trialkylamines and acid‐containing (meth)acrylates

Polymerizable ionic liquids were synthesized from the neutralization reaction between trialkylamines (tributylamine, trihexylamine, trioctylamine, 2‐(dimethyl‐amino)ethyl acrylate, and 2‐(dimethylamino)ethyl methacrylate) and acid‐containing (meth)acrylates to study the kinetics of their photopolymerization. The ionic liquids formed from acrylic acid and methacrylic acid with trialkylamines showed low or moderate increases in rate compared to their monofunctional analogues. The ionic liquids formed from (meth)acrylic acid and a tertiary amine with a pendant acrylate exhibited rates typical of traditional di(meth)acrylates, although the (meth)acrylates were not covalently attached to the same molecule. All of the phosphate‐based ionic liquids exhibited very rapid polymerization rates and strong dependence on the initial viscosity. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3009–3021, 2007     

Correlation between local mobility and mechanical properties of high‐speed melt‐spun nylon‐6 fibers

This article establishes the processing–microstructure–motion–property relationship of high‐speed melt‐spun nylon‐6 fibers. From solid‐state ¹H NMR T_1ρ (spin–lattice relaxation time in the rotating frame) relaxation studies, all nylon‐6 fibers spun at 4500–6100 m/min showed three‐component exponential decay with the time constants T_1ρ,I, T_1ρ,II, and T_1ρ,III, indicating that there existed three different motional phases. These phases were assigned to immobile crystalline, intermediate rigid amorphous, and mobile amorphous regions. The determination of the correlation time (τ_c) of the respective phases provided information about the local molecular mobility of each phase with respect to the spinning speed. As the spinning speed increased, τ_c of the crystalline region increased (4500–5200 m/min) and then reached a plateau. However, τ_c for the rigid amorphous region increased from 5200 m/min onward, indicating that the rigid amorphous chains were more oriented and constrained in the spinning speed range of 5500–6100 m/min. The drastic increase of the maximum thermal stress for all fibers from 5500 to 6100 m/min was coincident with the τ_c characteristics of the rigid amorphous region. The significant increase in tenacity and Young's modulus and the large decrease in elongation at break at 5500–6100 m/min were also in good agreement with the local molecular motion of the intermediate rigid amorphous phase in the nylon‐6 fibers. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 993–1000, 2001     

Correlation between static mechanical properties of starch-glycerol materials and low-temperature relaxation

Mechanical, calorimetric, dynamic mechanical and dielectric properties were measured in starch and amylose films plasticized by different glycerol contents. Low-temperature relaxation was found to be highly dependent on plasticizer level and related to unusual mechanical properties.     

Synthesis and characterization of physically crosslinked N‐vinylcaprolactam,acrylic acid,methacrylic acid,and N,N‐dimethylacrylamide hydrogels

Physically crosslinked hydrogels based on N‐vinylcaprolactam/acrylic acid and N‐vinylcaprolactam/methacrylic acid were prepared via free radical polymerization. These temperature responsive hydrogels were characterized in terms of glass transition, phase separation temperature, potentiometric titration and swelling properties. Results showed that phase transition temperature was dependent on the pH value of the solution; increasing pH led to higher lower critical solution temperature (LCST) values which was related to the dissociative behaviors of the carboxylic group of MAc in the buffered solutions. Additionally, with the incorporation of N,N‐dimethylacrylamide into the system, cloud point measurements and MDSC showed an increased in the LCST. This increase was based on hydrophilicity, the hydrophilic–hydrophobic balance was disturbed, and consequently, the LCST behavior was shifted. The pKa of the copolymers ranged between 5.6 and 6.5, while for the terpolymers pKa ranged between 5.3 and 6. At high pH (>10), the ? COOH group is deprotonated and negatively charged (? COO^?), while at low pH (1–3) the carboxylic group remains protonated which results in hydrogen bonding between the hydroxyl groups (from NaOH) and the excess of HCl. These results correlate with swelling studies where above the pKa value the hydrogels dissolved rapidly compared to below pKa they did not dissolve at all. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1555–1564     

Irradiation ageing of CSPE/EPR control command electric cables. Correlation between mechanical properties and oxidation

In this paper, correlations between the elongation at break and the oxidation of chlorosulfonated polyethylene and ethylene propylene rubber (EPR) polymers in instrumentation and control cables irradiated at different dose rates are brought to evidence. During irradiation, the following phenomena are observed: an increase of oxygen consumption, a degradation of the mechanical properties and a reduction of the oxidation induction time (OIT) measured for EPR.

A correlation between the mechanical properties and the OIT of the EPR has only been established in the case of irradiation at low dose rate. This reveals a difference in the oxidative degradation process at low and high dose rates. This study shows the possibility to assess the ageing of electric cables installed inside nuclear power plants by OIT measurements.