One component photo‐curing agent for epoxy resins based on multifunctional photobase generators containing oxime–urethane groups

In order to develop a one‐component photo‐curing system for epoxy resin, the photo‐crosslinking reactions of the diglycidyl ether of bisphenol A (DGEBA) in the presence of a multifunctional photobase generator (PBG) containing oxime–urethane groups were studied. The cross‐linking of DGEBA films and adhesion properties of DGEBA formulations containing the PBG and benzophenone increased with irradiation dose, post‐exposure baking (PEB) time, PEB temperature, and the number of oxime–urethane groups in the PBG. A synergistic effect was observed between the PBG and a base amplifier on the film cross‐linking of DGEBA. A trifunctional PBG containing oxime–urethane groups was found to be the most efficient PBG in terms of the photo‐crosslinking and adhesion properties of the DGEBA‐based formulations. Moreover, the devised formulations, including the PBG and benzophenone, were stable for at least 1 month at room temperature. The photocuring system developed in this study appears to offer a one‐pack epoxy resin curing system with practical useful properties. Copyright © 2009 John Wiley & Sons, Ltd.     

Photoresponsive water‐dispersible polyaniline nanoparticles through template synthesis with copolymer micelle containing coumarin groups

A novel kind of photosensitive water‐dispersible polyaniline (PANI) nanoparticles was designed and prepared by template synthesis using a photo‐responsive vinyl‐coumarin (VM)/2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPS) copolymer micelle containing coumarin moieties. The resulting PANI nanoparticles exhibited reversible photo‐crosslinking and photo‐decrosslinking behavior similar to coumarin moiety upon irradiation with different UV light as verified by UV–vis absorption. In addition, photoinduced size change of the PANI nanoparticles after 365 nm UV light irradiation was successfully monitored by dynamic light scattering and transmission electron microscopy measurements, further confirming the photosensitivity of the obtained PANI nanoparticles by the incorporation of VM/AMPS copolymer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Kinetics of photocrosslinking reactions of a DCPA/EA matrix in the presence of thiols and acrylates

The crosslinking efficiency and kinetics of a solid acrylic copolymer DCPA/EA (dicyclopentenyl acrylate/ethyl acrylate) matrix were investigated in the presence of pentaerythritol tetrakis (2-mercaptoacetate) (PETMP) or pentaerythritol tri- and tetraacrylates used as multifunctional crosslinking agents. The reaction of thiol and acrylate addition was sensitized by benzophenone (BP). The crosslinking efficiency of the DCPA/EA—BP—PETMP copolymer system, illuminated at high wavelengths (λ > 310 nm), was compared with that of the DCPA/EA matrix alone and the 2-component system copolymer DCPA/EA–BP. The concentrations of photosensitizer and crosslinking agent were varied from 1 to 10 mass %. The kinetics of tetrafunctional thiol addition and cyclopentene (pendant group of the DCPA/EA matrix) disappearance was followed through Fourier transform infrared (FTIR) and by determining the gel content. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2333–2345, 1997     

Fluoropolyethers end‐capped by polar functional groups. IV. A novel approach to the evaluation of reactivities of hydroxy‐terminated ethoxylated fluoropolyethers in the tin(IV)‐catalyzed reactions with isophorone diisocyanate

The effect of catalyst dibutyltin dilaurate (DBTDL) on the kinetics of urethane formation reactions of α,ω‐bis(hydroxy)‐terminated fluoropolyethers Fomblin® Z‐DOL TXs (FPEs) of various molecular weights and poly(oxyethylene) glycol PEG‐400 with isophorone diisocyanate (IPDI) in hexafluoroxylene (HFX) and tetrahydrofuran (THF) at 40 °C and NCO:OH = 2:1 have been studied in a broad range of catalyst (0.10–9.00) ×10^?4 M and total reagents (10.0–60.1 wt %) concentrations. The rate of tin‐catalyzed second‐order reactions (with respect to diol and diisocyanate) was found to be proportional to the square root of catalyst concentration [DBTDL]^0.5 both in low polar (HFX) and polar (THF) solvents. Effect of catalyst saturation was revealed for all the reaction systems at higher DBTDL concentrations as well as the appearance of the limiting catalyst concentrations C_lim below which the rates of reaction were close to zero. Based on these findings new effective rate coefficients have been derived k = k_cat/(C ? C) that are independent of the total reagent concentration in the range of 10.0–60.1 wt % ([OH] = 0.10–0.91 equiv/L). This new approach highlights that the rate of the tin‐catalyzed urethane formation reactions of α,ω‐bis(hydroxy)‐terminated fluoropolyethers Z‐DOL TXs with IPDI in HFX at 40 °C and NCO:OH = 2:1 increases significantly with increasing MW of FPE from 776 up to 3405. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5354–5371, 2004     

Determination of thermodynamic properties of macroporous glycidyl methacrylate‐based copolymers by inverse gas chromatography

Macroporous crosslinked poly(glycidyl methacrylate‐co‐ethylene glycol dimethacrylate) (PGME) was synthesized by suspension copolymerization and modified by ring‐opening reaction of the pendant epoxy groups with ethylene diamine (EDA). Inverse gas chromatography (IGC) at infinite dilution was applied to determine the thermodynamic interactions of PGME and modified copolymer, PGME‐en. The specific surface areas of the initial and modified copolymer samples were determined by the BET method, from low‐temperature nitrogen adsorption isotherms. The specific retention volumes, V, of 10 organic compounds of different chemical nature and polarity (nonpolar, donor, or acceptor) were determined in the temperature range 333–413 K. The weight fraction activity coefficients of test sorbates, , and Flory–Huggins interaction parameters, , were calculated and discussed in terms of interactions of sorbates with PGME and PGME‐en. Also, the partial molar free energy, , partial molar heat of mixing, , sorption molar free energy, ΔG, sorption enthalpy ΔH, and sorption entropy, ΔS, were calculated. Glass transitions in PGME and PGME‐en, determined from IGC data, were observed in the temperature range 373–393 K and 363–373 K, respectively. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2524–2533, 2005     

Consistency of theory and experiment in the ethane–methyl radical system

The thermal decomposition of ethane has been reinvestigated using the single pulse, reflected shock technique. Reflected shock temperatures were corrected for boundary layer-induced nonidealities using the thermal decomposition of cyclohexene as a kinetic standard. The rate constant for the reaction was calculated from the rate of formation of methane under conditions of very low extent of reaction, over a temperature range of 1000–1241 K. Ethane compositions of 1% and 3% in argon at total reaction pressures of 3 and 9 atm were used, and a small pressure dependence of k₁ was observed. An RRKM model is described which gives excellent agreement with this and other recent dissociation and recombination rate constant data in light of a recent revision to the thermochemistry of the methyl radical. In the range of 1000–1300 K an RRKM extrapolated k is given by the expression, log k = 17.2 ? 91,000/2.3RT, while at 298 K the calculation gives log k (l/mol sec) = 10.44, where k is calculated from k and the equilibrium constant.     

Electrochemical,spectroscopic, and thermal studies on interactions of linear poly(acrylic acid) with uranyl ions in aqueous solutions

The formation of complexes between linear poly(acrylic acid) (PAA) and uranyl ions in aqueous solutions was studied with conductometry, potentiometry, thermal analysis, Fourier transform infrared, and luminescence spectroscopy methods. The stoichiometry of the PAA/UO complex on repeating units of a PAA basis was determined to be 2:1. IR spectroscopy studies made on solid complexes showed that the carbonyl stretching absorption band of PAA was shifted to a higher wave number, and a new band at 1749 cm^?1 in the polycomplex spectrum was observed, confirming the existence of specific interactions between the carboxylate groups of PAA and metal ions. Luminescence spectroscopy studies showed an increase in the intensity of the uranyl‐ion emission spectra and new band formation at 483 nm, further confirming the interaction of UO ions with PAA in aqueous solutions. The thermal behavior of PAA/UO complexes further proved strong interactions in the complex structure. The thermal degradation of the polycomplexes included the main stages of destruction of both PAA and uranyl nitrate. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1610–1618, 2004     

Unperturbed dimensions of random and alternating styrene/n-alkyl methacrylate copolymers

The steric factors σ of homopolymers of ethyl, n-butyl, and n-octyl methacrylate, of equimolar random and alternating copolymers of these monomers with styrene, and of polystyrene, were determined by measuring intrinsic viscosities in a good solvent (butanone, 25°C) and extrapolating the data thus obtained to zero molecular weight of the polymer. For all comonomeric pairs under investigation, the σ² of an equimolar random copolymer and, particularly, of an alternating copolymer, is higher than the arithmetic mean (σ + σ)/2 of the σ² values of the parent homopolymers. The positive deviation from the linear dependence of σ² on the copolymer composition, expressed as an increment of σ², is proportional to the mole fraction of alternating dyads in the copolymer chain with in the limits of experimental error. The effect of copolymer microstructure on the unperturbed dimensions of the chains has been compared for equimolar copolymers of styrene with methyl, ethyl, n-butyl, and n-octyl methacrylate by using a relative increment ξ defined as the ratio of σ² of the alternating copolymer to (σ + σ)/2. The dependence of ξ on the number of carbon atoms in the alcohol substituent of the methacrylate component of the copolymer seems to exhibit a maximum for ethyl methacrylate.     

Sequential photodecomposition of bisacylgermane type photoinitiator: Synthesis of block copolymers by combination of free radical promoted cationic and free radical polymerization mechanisms

A block copolymer of cyclohexene oxide (CHO) and styrene (St) was prepared by using bifunctional visible light photoinitiator dibenzoyldiethylgermane (DBDEG) via a two‐step procedure. The bifunctionality of the photoinitiator pertains to the sequential photodecomposition of DBDEG through acyl germane bonds. In the first step, photoinitiated free radical promoted cationic polymerization of CHO using DBDEG in the presence of diphenyliodonium hexafluorophosphate (Ph₂I⁺PF) was carried out to yield polymers with photoactive monobenzoyl germane end groups. These poly(cyclohexene oxide) (PCHO) prepolymers were used to induce photoinitiated free radical polymerization of styrene (St) resulting in the formation of poly(cyclohexene oxide‐block‐styrene) (P(CHO‐b‐St)). Successful blocking has been confirmed by a strong change in the molecular weight of the prepolymer and the block copolymer as well as NMR, IR, and DSC spectral measurements. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4793–4799, 2009     

Kinetics of crosslinking reactions. 2. Reaction rates of intermolecular and intramolecular crosslinkings by using a soluble microgel

Soluble microgels with several pendant vinyl groups were synthesised by radical copolymerization of methyl methacrylate (MMA) with p-divinyl benzene (p-DVB). The competitive reactions of intermolecular and intramolecular crosslinkings of these microgels were carried out at 40°C in the presence of 1-buten-3-ol as a degradative chain transfer agent. The rate constant of intermolecular crosslinking (k) was estimated by GPC (gel permeation chromatography) analysis on the polymer produced from intermolecular propagation between bimolecules. The k depended strongly on the internal structure of microgels. Network formation was discussd inclusive of informations for the rate constant of intramolecular crosslinking (k).     

Structure and viscoelasticity of matched asymmetric diblock and triblock copolymers in the cylinder and sphere microstructures

A polystyrene–polyisoprene (PS–PI) diblock copolymer (10,000–50,000 g/mol) and a matched PS&ndashPI–PS triblock (10,000–100,000–10,000 g/mol) were employed to study the effect of chain architecture on the rheological response of ordered block copolymer melts. Both samples adopt hexagonal microstructures with PS cylinders embedded in a PI matrix; on further heating, an order–order transition (OOT) into a cubic array of spheres takes place prior to the order–disorder transition. Each morphology was verified by SAXS and TEM. Interestingly, at the OOT the low-frequency elastic modulus of the diblock increased abruptly, whereas that of the triblock decreased. In contrast, the modulus of the cubic phase was roughly independent of chain architecture. Chain relaxation parallel and perpendicular to the cylinders was probed by measuring the elastic modulus of a macroscopically aligned sample in directions parallel G and perpendicular (G) to the cylinder orientation. For both materials G < G < G where G is the elastic modulus of a randomly oriented sample. This result is attributed to the ability of the unentangled PS blocks to move along the direction of the cylinder axis, and thus relax the stress in the PI matrix in the parallel alignment. In each of the three cylindrical orientations the triblock had a larger modulus than the diblock, which is attributed to the presence of bridging PI blocks that connect distinct PS domains. About 20° below the OOT G showed a distinct change in its temperature dependence, which, coupled with SAXS measurements, is indicative of the onset of an undulation in the cylinder diameter that presages the pinching off of cylinders into spheres, as recently predicted by theory. The use of oriented samples also permitted SAXS confirmation of an approximate epitaxial relationship between the cylinder and the sphere unit cells, although a distinct change in the location of the structure factor maximum, q^*, is noted at the OOT. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2811–2823, 1997     

New simple method of measuring the surface glass transition temperature of polymers

A lap‐shear joint mechanical testing method has been probed to measure the surface glass transition temperature (T) of the thick bulk films of high‐molecular‐weight polymers. As T, the temperature transition “occurrence of autoadhesion–nonoccurrence of autoadhesion” has been proposed. The influence of chain flexibility, of molecular architecture, of polymer morphology, and of chain ends concentration on the T has been investigated. The correlation between the reduction in T with respect to the glass transition temperature of the bulk (T) and the intensity of the intermolecular interaction in the polymer bulk in amorphous polymers has been found. The effect of surface roughness on T has been discussed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2012–2021, 2010     

Intrinsic birefringence of poly(trimethylene terephthalate)

Highly oriented poly(trimethylene terephthalate) (PTT) fiber has a low birefringence that is unexpected for an aromatic polyester with a high refractive index. To explain this observation, the intrinsic birefringence Δn of PTT crystal was calculated from its bond polarizabilities to be 0.029. This Δn is almost an order of magnitude smaller than poly(ethylene terephthalate)'s value at 0.22, although both polymers have nearly identical crystal refractive indices. The small Δn is due to the arrangement of PTT's methylene groups in gauche conformations, causing the chain‐repeating unit to be tilted ～53° away from the c axis toward the basal plane. Because of the small Δn, the crystalline‐phase orientation made only a small contribution to the overall birefringence despite the fiber's high crystallinity and orientation. To understand the effect of the number of methylene groups on polyester optical anisotropy, the Δn's of a series of poly(m‐alkylene terephthalates) with m = 2–5 were compared and correlated with ψ: an angle made by the normal of the benzene ring with the crystal's axis. As ψ′ decreases, Δn of the polyesters diminishes. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1513–1520, 2002     

Synthesis and characterizations of well‐defined branched polymers with AB2 branches by combination of RAFT polymerization and ROP as well as ATRP

A well‐defined branched copolymer with PLLA‐b‐PS₂ branches was prepared by combination of reversible addition‐fragmentation transfer (RAFT) polymerization, ring‐opening polymerization (ROP), and atom transfer radical polymerization (ATRP). The RAFT copolymerization of methyl acrylate (MA) and hydroxyethyl acrylate (HEA) yielded poly(MA‐co‐HEA), which was used as macro initiator in the successive ROP polymerization of LLA. After divergent reaction of poly(MA‐co‐HEA)‐g‐PLLAOH with divergent agent, the macro initiator, poly(MA‐co‐HEA)‐g‐PLLABr₂ was formed in high conversion. The following ATRP of styrene (St) produced the target polymer, poly(MA‐co‐HEA)‐g‐(PLLA‐b‐PS₂). The structures, molecular weight, and molecular weight distribution of the intermediates and the target polymers obtained from every step were confirmed by their ¹H NMR and GPC measurements. DSC results show one T = 3 °C for the poly(MA‐co‐HEA), T = ?5 °C, T= 122 °C, and T = 157 °C for the branched copolymers (poly(MA‐co‐HEA)‐g‐PLLA), and T = 51 °C, T = 116 °C, and T = 162 °C for poly(MA‐co‐HEA)‐g‐(PLLA‐b‐PS₂). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 549–560, 2006     

A novel photosensitive ternary complex consisting of phenol‐formaldehyde resin,sodium dodecyl sulfate,and diazo resin

A novel photosensitive ternary complex formed from phenol‐formaldehyde resin (PR), sodium dodecyl sulfate (SDS), and diazo resin (DR) was developed. In the presence of SDS, PR remains soluble in water when its solution is neutralized. The PR‐SDS‐DR ternary complex forms when DR is added to the PR‐SDS solution. The ternary complex dissolves in polar solvents such as dimethylformamide and is sensitive toward UV light or heating. It was confirmed that the ionic bond of  SO +N₂ between SDS and DR converts to a covalent bond after the decomposition of the ⁺N₂ group under UV irradiation or heating. As a result, the solubility of PR‐SDS‐DR changes dramatically; that is, after treatment with UV light or heating, PR‐SDS‐DR becomes insoluble in polar solvents. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2566–2571, 2000     

Preparation of exfoliated polyacrylic clay nanocomposites with high loading: An investigation into the intercalation of ammonium‐terminated polyacrylic acid and polyacrylates

Low‐molecular‐weight polyacrylic acid with amine chain end used as a macromolecular intercalating agent was synthesized by radical polymerization using 2‐aminoethanethiol hydrochloride as chain transfer agent. Three polyacrylates (sodium polyacrylate‐t‐NH, calcium polyacrylate‐t‐NH, and zinc polyacrylate‐t‐NH) were prepared by neutralization from this polyacrylic acid using sodium hydroxide, zinc oxide, and calcium hydroxide as alkalies. The intercalation of ammonium‐terminated polyacrylic acid and polyacrylate was investigated by viscosity measurement, XRD, and TEM. Using this ammonium‐terminated polyacrylic acid as the intercalating agent, exfoliated polyacrylic acid/clay and polyacrylate/clay composites with a clay loading of ～30 and 20 wt %, respectively, were prepared through the evaporation of solvent from their clay suspensions. The thermal degradation of polyacrylic acid/clay and polyacrylate/clay composites was also studied by TGA. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2335–2340, 2008     

Chiral 2-Aryl-2-methyl-2H-1-benzopyrans: Synthesis,characterization of enantiomers,and barriers to thermal racemization

The ease of thermal breaking of the C(sp³)? O bond of the 2-aryl-2-methyl-2H-1-benzopyrans 1 – 9 was evaluated by measuring the free energy (ΔG) of the racemization reaction of optically active compounds. The variation of ΔG of the thermal ring opening in terms of structural modifications is discussed. The synthesis of the studied compounds, the preparative separation of enantiomers by liquid chromatography, the determination of enantiomeric purity, the circular dichroism of enriched enantiomers, and the measurement of rate constants of enantiomerization by monitoring the decrease of the polarimetric angle of rotation at suitable temperatures are described.     

Effects of salts and copolymer composition on the lower critical solution temperature of poly(methyl 2‐acetamidoacrylate‐co‐methyl methacrylate) solutions

Copolymerizations of methyl 2‐acetamidoacrylate (MAA) with methyl methacrylate (MMA) were carried out at 60 °C in chloroform. Copolymers containing MAA units in the range of 83–90 mol % exhibited a lower critical solution temperature (LCST), although homopolymers of MAA and MMA did not. The LCST of polymer solutions decreased with (1) an increase in the concentration of the copolymer, (2) a decrease in the MAA content in the copolymer, and (3) an increase in the concentration of salts added. The effectiveness of anionic species for reducing the LCST is NO < Cl^? < SO < SO. Divalent anion is more effective for lowering the LCST than monovalent anion. However, there is no difference between cationic species in the salting‐out effect. Sodium carbonate and sodium phosphate had a salting‐in effect. Salting‐out coefficients were evaluated from the relationship between the logarithm of solubility of the copolymers and the salt concentration. Salting‐out coefficients of the copolymer depended not on the composition of the copolymers but on the salt added. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1945–1951, 2002     

Network formation of a phenyl vinyl ketone copolymer with 4-vinylbenzil and its photodecrosslinking in films

The irradiation (λ > 400 nm) in air of a copolymer of phenyl vinyl ketone with 4-vinylbenzil (VBZ) containing 1.5 wt % VBZ structural units in film, followed by the thermal decomposition of the resulting pendant benzoyl peroxide groups, leads to crosslinking. The subsequent irradiation of the crosslinked polymer at 366 nm results in the cleavage of the poly(phenyl vinyl ketone) chain between the junction points of the polymer network through a Norrish type II reaction. Therefore, poly(phenyl vinyl ketone-co-4-vinylbenzil) represents a novel type of photoresist based on polymer network decrosslinking. The process involves three steps: photogeneration of peroxide, crosslinking by its thermal decomposition, and subsequent photodecrosslinking of the polymer network. This material provides positive-tone images after UV exposure (λ > 330 nm) and development in an organic medium such as isopropyl methyl ketone. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 765–771, 2004     

Non‐transition metal‐catalyzed living radical polymerization of vinyl chloride initiated with iodoform in water at 25 °C

Non‐transition metal‐catalyzed living radical polymerization (LRP) of vinyl chloride (VC) in water at 25–35 °C is reported. This polymerization is initiated with iodoform and catalyzed by Na₂S₂O₄. In water, S₂O dissociates into SO that mediates the initiation and reactivation steps via a single electron transfer (SET) mechanism. The exchange between dormant and active propagating species also includes the degenerative chain transfer to dormant species (DT). In addition, the SO₂ released from SO during the SET process can add reversibly to poly(vinyl chloride) (PVC) radicals and provide additional transient dormant ～SO radicals. This novel LRP proceeds mostly by a combination of competitive SET and DT mechanisms and, therefore, it is called SET‐DTLRP. Telechelic PVC with a number‐average molecular weight (M_n) = 2,000–55,000, containing two active ～CH₂? CHClI chain ends and a higher syndiotacticity than the commercial PVC were obtained by SET‐DTLRP. This PVC is free of structural defects and exhibits a higher thermal stability than commercial PVC. SET‐DTLRP of VC is carried out under reaction conditions related to those used for its commercial free‐radical polymerization. Consequently, SET‐DTLRP is of technological interest both as an alternative commercial method for the production of PVC with superior properties as well as for the synthesis of new PVC‐based architectures. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6267–6282, 2004