Copolymerization kinetics of styrene/vinyl-ester systms: Low temperature reactions

Vinyl-ester (VE), synthesized by the addition reaction of methacrylic acid and diglycidyl ether of bis-phenol A (DGEBA) epoxy, and styrene react via bulk free radical chain growth copolymerization to form a crosslinked network polymer. Vital clues regarding the development and the structure of the network were obtained from the study of copolymerization kinetics of styrene/VE systems. Fourier transform infrared (FTIR) spectroscopy was used to obtain the individual fraction conversion rates of both the monomers. The conversion versus time data for both styrene and VE was fit to an autocatalytic kinetic model. The autocatalytic model was found to adequately replicate the kinetic data over the entire life of cure. In this investigation, the effects of styrene concentration, temperature, catalyst concentration, and initiator concentration on cure kinetics of styrene/VE systems were studied. The conversion profiles of both styrene and VE were used to obtain the reactivity ratios of the two monomers. The reactivity ratios were evaluated to be close to zero, suggesting that initially alternating copolymerization is favored over homopolymerization. The cure behavior of vinyl-ester resins is affected not only by the chemical reactivity of the monomers toward the free radicals, but also by diffusion effects, phase separation, and microgel formation. The interplay of these factors controls the kinetics of cure, thereby affecting the physical and chemical properties of the resulting polymer.     

Synthesis, characterization polymerization and antibacterial properties of novel thiophene substituted acrylamide

Ethyl 2-acrylamido-4,5,6,7-tetrahydrobenzo [b] thiophene-3-carboxylate (ETTCA) has been synthesized and its structure has been elucidated by elemental analysis and spectral tools. Free radical polymerization of (ETTCA) has been conducted in several solvents using azobisisobutyronitrile (AIBN) as an initiator. The kinetic parameters of polymerization of the ETTCA were investigated, and it was found that the polymerization reaction follows the conventional free radical scheme. The overall activation energy of polymerization ΔE was determined (ΔE = 45.11 kJ mol⁻¹). The copolymerization of ETTCA with three conventional monomers was carried out in dioxane at 65 °C. The monomer reactivity ratios for the copolymerization of ETTCA with methyl methacrylate (MMA), vinyl acetate (VA) and vinyl ether (VE) were calculated. Thermal stability of the ETTCA polymer and its copolymers were investigated by thermogravimetric analysis. It has been found that the prepared polymer (PETTCA) and its copolymers with VA have moderate biological activity and highly dependent on the copolymer composition.     

Allyl ether‐modified unsaturated polyesters for UV/air dual‐curable coatings. II: UV and air‐curing behavior

The photoinduced and peroxide‐induced polymerization behavior of dual‐curable allyl ether‐modified unsaturated polyester (AUPE) and vinyl ether (VE) used as a reactive diluent for dual‐curable coating have been studied by infrared spectroscopy (IR). For UV curing systems in N₂ atmosphere, the maleate's conversion and total conversion decrease with the increasing of allyloxy content. However, the rate and of copolymerization and conversion of VE are independent of allyloxy concentration. The copolymerization of allyl ether (AE) and vinyl ether occurs in the presence of maleate (MA) under UV irradiation. For air curing, the rate of copolymerization increases with allyloxy content. The ultimate conversion is the same irrespective of the allyloxy concentration. Because the electron‐rich double bond of allyloxy would become an electron‐deficient one through oxidation, the conversion of maleate decreases with increasing of the allyloxy content due to the enhancement of copolymerization of AE with VE. The ATR‐IR showed that different curing mechanisms occur in AUPE/VE system during air‐curing process. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2771–2776, 2004     

Free radical two step synthesis of styrene and acrylate block copolymers with disulphide initiators

Controlled two step block copolymerization of styrene, methyl methacrylate and ethyl acrylate with aliphatic and aromatic disulphides under UV irradiation took place in bulk and in THF solution. In the first step of the polymerization, the most reactive system was ethyl acrylate with aromatic disulphides. The molecular weights and yields of polymerizations increased with reaction time. The macromolecules were terminated by primary. SR radicals and by combination of two macroadicals which was observed by NMR spectroscopy. Aninsignificant portion of uninitiated photopolymerization was detected only for MMA. In the second step of polymerization, the purified macroinitiators from the first step reacted with additional monomers to form block copolymers with a small quantity of unreacted macroinitiator. The molecular weights of copolymers increased, the bonding segments between the blocks being detected by ¹H NMR. The overall reaction is an insertion of monomers between two thiyl groups.     

Photocuring systems composed of vinyl ether terminated polyurethane and maleate

Vinyl ether terminated polyurethane (VE–PU) was synthesized in this investigation. The copolymerization behavior of VE–PU and dimethyl maleate (DMA) was investigated by ¹³C‐NMR. It was found that the copolymerization of VE–PU and DMA is of alternating composition, and no homopolymer structure was found in the polymerization products. Differential photocalorimetry results show that, when the monomer feed molar ratio was close to 1 : 1, the total conversion increased, whereas the effective conversion decreased. The rate of copolymerization was affected by oxygen and reaction temperature and depended on the square root of both the initiator concentration and the light intensity. The rheological properties of VE–PU/DMA system were also studied. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1930–1935, 2005     

Microemulsion polymerization of styrene

Summary Heats of polymerization of three carbazolyl-containing epoxides 9-(2,3-epoxypropyl)carbazole, 1,2-epoxy-6-(9-carbazolyl)-4-oxahexane and 3,6-dibromo-9-(2,3-epoxypropyl) carbazole have been determined on the differential microcalorimeter DAK 1-1A (USSR). The influence of the structure of monomers upon the values of polymerization heat is discussed.     

Surface grafting of polymer onto carbon thin film

The surface grafting of polymers onto carbon thin film deposited on a glass plate was achieved by two methods: the graft polymerization initiated by initiating groups introduced onto the surface; and the trapping of polymer radicals by surface aromatic rings of the thin film. It was found that the radical and cationic graft polymerization of vinyl monomers are initiated by azo and acylium perchlorate groups introduced onto the surface, respectively, and the corresponding polymers are grafted onto the surface: the surface grafting of polymers were confirmed by the contact angle of the surface with water. In addition, the anionic ring-opening alternating copolymerization of epoxides with cyclic acid anhydrides was found to be initiated by potassium carboxylate groups on the carbon thin film to give the corresponding polyester-grafted carbon thin film. On the other hand, polymer radicals formed by the decomposition of azo polymer, such as poly(polydimethylsiloxane-azobiscyanopentanoate) and poly(polyoxyethylene-azobiscyanopentanoate), were successfully trapped by the surface aromatic rings of carbon thin film and polydimethylsiloxane and polyoxyethylene were grafted onto the surface. © 1995 John Wiley & Sons, Inc.     

(η6‐N‐alkylcarbazole) (η5‐cyclopentadienyl) iron hexafluorophosphate salts in photoinitiated and thermal epoxy polymerization

(η6‐Carbazole)(η5‐cyclopentadienyl) iron hexafluorophosphate salts (CFS PF₆) are capable of photoinitiating cationic polymerization of epoxy monomers directly upon irradiation with long‐wavelength UV light. To improve the solubility of CFS ferrocenium salts in epoxides, two CFS photoinitiators have been prepared: [cyclopentadiene‐Fe‐N‐buylcarbazole] hexafluorophosphate (C4‐CFS PF₆) and [cyclopentadiene‐Fe‐N‐octylcarbazole] hexafluorophosphate (C8‐CFS PF₆), bearing C4 and C8 alkyl chains, respectively, on the nitrogen atom. Studies with real‐time infrared spectroscopy have shown that C4‐CFS and C8‐CFS photoinitiators exhibit high efficiency in polymerization of 3,4‐epoxycyclohexylmethyl‐3,4‐epoxycyclohexane carboxylate (ERL‐4221) epoxy monomer, but lower efficiency in polymerization of di(2,3‐epoxypropyl)‐3,4‐epoxy‐1,2‐cyclohexanedioate (TDE‐85) epoxy monomer. Benzoyl peroxide (BPO) sensitizer was very effective in improving the photoinitiating activities of CFS in polymerization of both ERL‐4221 and TDE‐85. DSC studies have shown that C4‐CFS and C8‐CFS photoinitiators can also be employed as thermal initiators for the cationic ring‐opening polymerization of epoxides at moderate temperatures. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Photoinitiated alternating copolymerization of vinyl ethers with chlorotrifluoroethylene

The photoinitiated copolymerization of chlorotrifluoroethylene (CTFE) with several vinyl ethers [ethyl vinyl ether (EVE), 2‐chloroethyl vinyl ether (CEVE), cyclohexyl vinyl ether (CHVE), 4‐hydroxybutyl vinyl ether (HBVE)] was studied. CTFE is an acceptor monomer (e ～ 1.5) whereas vinyl ethers are donor monomers (e ～ ?1.5), and therefore their copolymerization led to alternating copolymers, as indicated by elementary analysis. The equilibrium constant (K_F) of the charge‐transfer complex formation (CTC) was determined by ¹⁹F NMR spectroscopy. Under our experimental conditions, K_F was low for CHVE/CTFE and HBVE/CTFE systems, 0.058 and 0.013 l mol^?1 respectively. It can be assumed that the copolymerization involves the free monomers rather than propagation via the donor–acceptor complex. The alternating structure arises from the great difference in polarity between the two types of monomers. Several functional copolymers were prepared in good yield and with molecular weight close to 15 000 g mol^?1. © 2002 Society of Chemical Industry     

Synthesis and polymerization of unsaturated derivatives of halogenated phenols

Summary The preparation of p-styrenesulfonic and methacrylic acid esters of the microbiocides 2, 4, 6-trichlorophenol and 4-chloro-m-cresol, and their characterization by IR, ¹H and ¹³C NMR spectroscopy are described. The radical homopolymerization of the biocidal monomers, and their copolymerization with various vinyl monomers have been studied. The polymerization gives polymers in which the microbiocide moieties are covalently attached to the polymer backbone chain by ester links.     

Survey of a catalyst system for living cationic polymerization of glucose‐carrying vinyl ethers with acetyl and isopropylidene protecting groups

This study concerns the living cationic polymerization of two vinyl ethers (VEs) having pendant glucose residues, in which the hydroxyl groups are protected by acetyl and isopropylidene functions. Living cationic polymerization of VE having an acetyl‐protected glucose was achieved by employing an initiating system consisting of the CF₃COOH adduct of isobutyl VE (IBVE) and ethylaluminium dichloride in the presence of an added base at 0 °C. In contrast, the use of the HCl adduct of IBVE in conjunction with zinc iodide at ?15 °C was more suitable for the controlled polymerization of VE having an isopropylidene‐protected glucose. Polymers obtained under these reaction conditions had narrow molecular weight distributions (M_w/M_n ～ 1.1) and controlled molecular weights. © 2001 Society of Chemical Industry     

Mechanistic aspects of sonochemical copolymerization of butyl acrylate and methyl methacrylate

This paper attempts to get a physical insight into the sonochemical emulsion copolymerization using butyl acrylate (BA) and methyl methacrylate (MMA) as model monomers at low to moderate ultrasound intensity. The principal physical mechanism underlying beneficial effects of ultrasound on emulsion polymerization system is cavitation, which affects the system in both chemical (i.e. generation of radicals that can initiate/propagate polymerization process) as well as physical (i.e. emulsification of reaction mixture) way. By taking dual approach of coupling experiments with simulations of cavitation bubble dynamics, we have tried to justify the trends in experiments results. The role of cavitation in the present study is found to be only physical. Quite interestingly, the chemical effect of cavitation is found to have no role to play. Reactivity ratios of both monomers for applied experimental conditions have been found to be less than 1, which hints at moderately alternating behavior of copolymerization. Theoretically calculated copolymer composition using the reactivity ratios of copolymers matched well with experimental values. The copolymer composition for all monomer feed ratios is rich in MMA, due to higher reactivity of MMA than BA. The molecular weight of the copolymer reduced with greater fraction of MMA in the reaction mixture. This effect is attributed to nature of termination of the BA (i.e., combination) and MMA (i.e., disproportionation) monomer radicals.     

Synthesis and properties of grafted latices from a soybean oil‐based waterborne polyurethane and acrylics

A novel soybean oil‐based vinyl‐containing waterborne polyurethane (VPU) dispersion has been successfully synthesized from toluene 2,4‐diisocyanate, dimethylol propionic acid and a 90 : 10 mixture of chlorinated soybean oil‐based polyol and acrylated epoxidized soybean oil (AESO). Then, a series of VPU/acrylic grafted latices have been prepared by emulsion graft copolymerization of acrylic monomers (40 wt % butyl acrylate and 60 wt % methyl methacrylate) in the presence of the VPU dispersion, using potassium persulfate as an initiator. The structure, morphology, and thermal and mechanical properties of the resulting latices, containing 15–60 wt % soybean oil‐based polyols as a renewable resource, have been investigated by Fourier transform infrared spectroscopy, solid state ¹³C NMR spectroscopy, transmission electron microscopy, thermogravimetric analysis, dynamic mechanical analysis, and mechanical testing. The results indicate that graft copolymerization of the acrylic monomers onto the VPU network occurs during emulsion polymerization, leading to a significant increase in the thermal stability and mechanical properties of the resulting miscible grafted latices. This work provides new environmentally‐friendly latices from a renewable resource with high performance for coating applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of the nature of monomers on the activity of supported titanium catalysts in the α-olefin polymerization

Summary Ethylene and propylene co-polymerization and sequential polymerization with high activity supported titanium catalysts were studied. Specific rate of homopolymerization and copolymerization constants for ethylene and propylene were determined by using the derived values of the solubility constants for monomers in nascent polymers. The reason of the increased rate of co-polymerization upon enriching the monomers mixture with propylene, the effect of activation of ethylene polymerization upon preliminary polymerization of propylene may be in the increasing number of active sites due to enlarged content of amorphous phase in the nascent polymer product.     

A systematic study of tert-butylacrylamide-methyl acrylate-acrylic acid radical solution terpolymerization

Multi-functional polymers used for personal care products can be synthesized by radical polymerization of acrylic acid (AA) in alcohol/water solutions with non-functional monomers such as methyl acrylate (MA) and N-tert-butylacrylamide (t-BuAAm). However, solvents capable of forming or disrupting hydrogen bonds cause the polymerization kinetics of these monomers to deviate from their polymerization behaviour in bulk and non-polar solvents. In this work, a previous mechanistic model developed for MA/t-BuAAm copolymerization is extended to represent the terpolymerization system MA/t-BuAAm/AA. The additional kinetic coefficients required for the system are estimated from fitting to AA homopolymerizations and AA/MA and AA/t-BuAAm copolymerizations conducted in an ethanol/water solution. In-situ nuclear magnetic resonance (NMR) spectroscopy is used to follow monomer conversions and composition drift behaviour, with the molar mass distributions of the polymer products characterized by size-exclusion chromatography. Although AA is more reactive than MA in non-polar solvents, the reactivities of the two monomers equalize under the experimental conditions examined. Thus, the batch and semi-batch terpolymerization data collected are represented equally well by a reduced acrylate/t-BuAAm copolymerization model and the full terpolymerization implementation.     

The synthesis and cationic polymerization of novel epoxide monomers

The preparation of a novel series of multifunctional silicon-containing epoxide monomers, oligomers, and polymers has been carried out. The hydrosilylation method employed was found to be applicable to the design and synthesis of a wide variety of materials with different chemical and mechanical characteristics, which range from hard and brittle to elastomeric. By tailoring the kinds of and number of epoxide groups that are incorporated into these materials, it is possible to substantially modify their reactivity in photoinitiated cationic polymerization. Those monomers and oligomers containing cycloaliphatic epoxide rings undergo polymerization rates considerably more rapid than conventional epoxides. There are many applications of such photocurable monomers in the field of electronic materials.     

The effect of monomer structure on oxygen inhibition of (meth)acrylates photopolymerization

Oxygen inhibition during the free-radical photopolymerization of various monomers containing ether groups was investigated using photo-DSC and real-time FTIR (RTIR). Methacrylates and acrylates containing different number and types of ether groups were selected to determine the effects of ether group concentration and structure on oxygen inhibition. Also, the oxygen sensitivity of the free-radical polymerization of methacrylate and acrylate was compared. Compared to acrylates, methacrylates are much less sensitive to oxygen. Model poly(tetramethylene oxide) and poly(propylene glycol) system were evaluated to determine the effect of ether groups on polymerization kinetics in air. The polymerizations of the (meth)acrylates containing ether groups were found to be relatively insensitive to oxygen inhibition. The reduction of oxygen inhibition occurs by a series of chain transfer/oxygen scavenging reactions.     

Matrix-induced variation in kinetics and control of molecular weight of methacrylic acid polymers during graft copolymerization with starch

Polymerization of synthetic monomers is known to be influenced by the solvent, initiator system, dilution, temperature, etc. Substrates like starch granules, when used for graft copolymerization, can be expected to provide a drastically different environment for the monomers (as compared to the bulk of the solvent medium), and therefore we predicted this to influence the kinetics of polymerization and stereoregularity of the synthetic polymer. This was investigated with respect to polymerization of methacrylic acid with starch. The rate of methacrylic acid polymerization was found to be significantly higher in grafting with starch as compared to homopolymerization in the absence of starch. Control of molecular weight of the grafted chains was achieved by use of chain transfer agents, and the chain transfer constants for graft copolymerization were determined for two chain transfer agents. The polydispersity of the grafted chains was also found to be dependent on the chain transfer agents. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 397–403, 1997     

Molecular design of novel network polymers

Cationic, anionic, and radical ring-opening polymerization of spiro and bicyclic monomers, and their application to network polymers have been developed. Bicyclo orthoesters (BOEs), spiro orthoesters (SOEs), and spiro orthocarbonates (SOCs) were polymerized by cationic double ring-opening. Bicyclobis(γ-butyrolactone)s and spirobis(γ-butyrolactone)s were copolymerized with epoxides by anionic alternating ring-opening. Polymers from SOCs bearing exomethylene groups consisted of ring-opened and vinyl polymerized units. The degree of ring-opening of SOCs depended upon the number of rings and steric hindrance. The radical polymerization of vinylcyclopropanone cyclic acetals depended on the ring-size. With the monomers bearing 5- and 6-membered acetal rings, single ring-opened polymers were obtained. With the monomer bearing 7-membered acetal ring, the polymer mainly consisted of double ring-opened unit. These monomers could be crosslinked by bifunctionalization. Poly(cyclic orthoester)s linked by covalent bonds with dithiols to bifunctional SOEs were crosslinked by acid catalysts, and the reversible crosslinking-depolymerization system could be controlled by temperature.     

Preparation and properties of alkoxysilane/acrylate copolymer microemulsion

A novel alkoxysilane/acrylate copolymer microemulsion was prepared by copolymerization of vinylmethyldiethoxysilane and acrylic monomers using a composite emulsifier system composing of ordinary anionic sodium dodecyl sulphate (SDS), nonionic po1yoxyethylene octylphenol ether (OP-10), and n-butanol as co-surfactant, ammonium persulfate (APS) as initiator. The effects of polymerization processes, reaction conditions and the polymer content on the copolymer microemulsion were investigated, respectively. The structure of the copolymer was characterized by FT-IR spectroscopy. FT-IR spectrum analysis of the latex film indicated that copolymerization occurred. The morphology and size of the microlatex particles had been characterized by TEM and photon correlation spectroscopy (PCS), respectively. Results showed that seeded microemulsion polymerization with a high temperature emulsification process was superior for producing stable copolymer microlatexes. With high alkoxysilane content (30 wt.%), high copolymer content (37.5 wt.%) and low emulsifiers content (5 wt.%), the nanoparticles in the range from 20 nm to 60 nm were obtained.