Preparation of hyperbranched polymers through ATRP of in situ formed AB* monomer

The self‐condensing vinyl polymerization of an AB* monomer formed in situ by atom transfer radical addition from divinylbenzene (DVB) and (1‐bromoethyl)benzene (BEB) using atom transfer radical polymerization technique was studied. The catalyst concentration has a dramatic effect on polymerization. To study the polymerization mechanism and to achieve high molecular weight polymer, the polymerization was carried out in bulk with a catalyst to monomer ratio, 2,2′‐bipyridine to DVB, of 0.2 at 90°C. Proton nuclear magnetic resonance (¹H NMR) spectroscopy and size‐exclusion chromatography coupled with multiangle laser light scattering were used to analyze the polymerization aliquots and the obtained polymer. The intrinsic viscosities of the prepared polymers were also measured. Experimental results, from the comparison of the apparent molecular weights measured by size‐exclusion chromatography with the absolute values measured by multiangle laser light scattering as well as viscosity measurements, indicate the existence of hyperbranched structures in the prepared polymers. In sharp contrast to hyperbranched polymers from AB* monomer preprepared, hyperbranched ploy(divinylbenzene) prepared at equimolar amount of DVB and BEB has numerous residual pendant vinyl groups rather than only one double bond at its focal point. The hyperbranched polymers show relatively narrow molecular weight distribution (2.13–3.77) and exhibit excellent solubility in common organic solvents such as acetone. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 850–856, 2006     

Preparation and characterization of hyperbranched polyacrylate copolymers by self‐condensing vinyl copolymerization (SCVCP)

A series of hyperbranched polyacrylate copolymers have been synthesized by self‐condensing vinyl copolymerization (SCVCP) of 2‐(2‐bromopropionyloxy)‐ethyl acrylate (BPEA) and methyl acrylate (MA) in the presence of CuBr and bipyridine. The structures and properties of the polymers obtained are characterized by NMR and SEC/RALLS/DV/RI measurements. The effects of reaction conditions on molecular weight (MW), molecular weight distribution (MWD) and degree of branching (DB) are investigated. © 2002 Society of Chemical Industry     

Studies on the preparation of branched polymers from styrene and divinylbenzene

The self‐condensing vinyl polymerization of styrene and an inimer formed in situ by atom transfer radical addition from divinylbenzene and 2‐bromoisobutyl‐tert‐butyrate using atom transfer radical polymerization technique was studied. To study the polymerization mechanism and achieve high molecular weight polymer in a high polymer yield, the polymerization was carried out in bulk at 80°C. Proton nuclear magnetic resonance (¹H‐NMR) spectroscopy and gel permeation chromatography (GPC) coupled with multiangle laser light scattering (MALLS) were used to monitor the polymerization process and characterize the solid polymers. It is proved that the polymerization shows a “living” polymerization behavior and the crosslinking reaction has been restrained effectively due to the introduction of styrene. Polymers with high molecular weight (M_w.MALLS > 10⁵) can be prepared in high yield (near 80%). Comparison of the apparent molecular weights measured by GPC with the absolute values measured by MALLS indicates the existence of branched structures in the prepared polymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

A tough noncombustible material prepared by grafting of poly(2‐ethylhexyl acrylate) with vinyl chloride

A noncombustible tough poly(vinyl chloride) (tPVC) was prepared by suspension‐grafted copolymerization of poly(2‐ethylhexyl acrylate) (poly‐EHA; elastomer) with vinyl chloride (VC). Elastomer (poly‐EHA) was prepared by emulsion, mainly homopolymerization of 2‐ethylhexyl acrylate at a temperature of 30 ± 0.1°C in the presence of a redox system and with the advantage of dosing the monomer into two portions. Grafted‐suspension copolymerization of poly‐EHA with VC was carried out at 54 ± 0.1°C, keeping other reaction conditions only slightly modified in comparison with those for the polymerization of pure VC. An optimum content of the incorporated poly‐EHA in PVC was found to be in the range 7.5–8.5 wt %, whereas notched toughness of 85–87 kJ m^?2 was reached. Both below and above the found range of the content of poly‐EHA, the toughness decreases. A copolymer prepared by a direct‐emulsion copolymerization of 2‐EHA and VC (poly‐EHA‐co‐VC) exhibited worse mechanical properties than the copolymer prepared by two polymerization steps. On the basis of experimental results, effects of the reaction procedure on the properties of resulting material are described. In addition to good mechanical properties, tPVC also shows its noncombustibly. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2355–2362, 2002     

Synthesis and characterization of hyperbranched poly(ethyl methacrylate) by quasi‐living radical polymerization of photofunctional inimer

The hyperbranched poly(ethyl methacrylate)s (PEMAs) were prepared by the quasi‐living radical polymerization of 2‐(N,N‐diethylaminodithiocarbamoyl)ethyl methacrylate (DTCM). DTCM monomer plays an important role in this polymerization system as an inimer that is capable of initiating quasi‐living radical polymerization of the vinyl group. Hyperbranched PEMAs with relatively narrow polydispersity ( M _w/ M _n ≈ 1.6) were obtained. The compact nature of the hyperbranched PEMAs is demonstrated by solution properties which are different from those of the linear analogues. © 2002 Society of Chemical Industry     

Atom transfer radical polymerization and copolymerization of vinyl acetate catalyzed by copper halide/terpyridine

Copper‐mediated atom transfer radical polymerization (ATRP) is versatile for living polymerizations of a wide range of monomers, but ATRP of vinyl acetate (VAc) remains challenging due to the low homolytic cleavage activity of the carbon‐halide bond of the dormant poly(vinyl acetate) (PVAc) chains and the high reactivity of growing PVAc radicals. Therefore, all the reported highly active copper‐based catalysts are inactive in ATRP of VAc. Herein, we report the first copper‐catalyst mediated ATRP of VAc using CuBr/2,2′:6′,2″‐terpyridine (tPy) or CuCl/tPy as catalysts. The polymerization was a first order reaction with respect to the monomer concentration. The molecular weights of the resulting PVAc linearly increased with the VAc conversion. The living character was further proven by self‐chain extension of PVAc. Using polystyrene (PS) as a macroinitiator, a well‐defined diblock copolymer PS‐b‐PVAc was prepared. Hydrolysis of the PS‐b‐PVAc produced a PS‐b‐poly(vinyl alcohol) amphiphilic diblock copolymer. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Relationship between mechanical properties of ceramic green body and structures of photo-cured acrylate polymer for ceramic 3D printing based on photo polymerization

3D printing technologies using photo polymerization of photo-curable monomer and oligomers as an organic binder have been studied to fabricate ceramics with a complicated shape. For minimizing distortion of ceramics during the manufacturing process and fast 3D printing of ceramic green body, high mechanical strength of ceramic green body and fast photo polymerization of the photo-curable resin are required, respectively. In this study, the ceramic green bodies with various compositions were fabricated by photo radical polymerization of the slurry-type resin composed of fused silica bead, and tri- or (and) mono-functional acrylate. Photo radical polymerization behaviors of mono-, tri-functional acrylate monomer, and blend of two monomers were analyzed by photo-DSC and FT-IR measurements. The structure analysis of photo-cured polymers made by each monomer was performed by thermo-mechanical analysis. Through mixing of mono- and tri-functional acrylate monomer, we confirmed that polymerization rate more increased compared with those of only mono-, tri-functional monomer. Unreacted vinyl groups in the polymers prepared with blend of two monomers decreased by an addition of mono-functional monomer in tri-functional monomer. The polymers prepared with the blend showed higher storage modulus and broader viscoelastic behavior compared to those fabricated with tri-functional monomer. Thus, to achieve high fracture strength of the green body, we verified that the photo-cured polymer in the green body should have high crosslinking density and low free volume based on reduction of unreacted vinyl groups in the polymer. Additionally, through analysis of cross-sectional SEM of the green body, we confirmed that acrylate monomer should include proper content in the slurry-type resin to maximize the fracture strength of the body regardless of the type of the used acrylate monomer. This was because low content of acrylate monomer in the slurry-type resin makes it difficult to form neckings composed with photo-cured polymers between the silica beads.     

Hyperbranched polyacrylates prepared by self‐condensing vinyl copolymerization in the presence of a tetrafunctional initiator

Hyperbranched copolymers were synthesized by self‐condensing vinyl copolymerization (SCVCP) of 2‐[(2‐bromopropionyl)oxy]ethyl acrylate (BPEA) and methyl acrylate (MA) in the presence of a tetrafunctional initiator, 6,6‐bis[5‐(α‐bromoisobutyryloxy)‐2‐oxapentyl]‐4,8‐dioxaundecane‐yl‐1,11 dibromoisobutyrate (THABI). The structures of the polymers obtained were characterized by NMR and size exclusion chromatography/right‐angle laser‐light scattering/differential viscometry/differential refractometry. Molecular weight, molecular weight distribution and degree of branching were influenced by conversion and initial feed molar ratio of BPEA, MA and THABI. The addition of THABI can narrow the polydispersity of the hyperbranched copolymers obtained. The results are consistent with our previous simulation work. © 2003 Society of Chemical Industry     

Preparation of branched polyacrylonitrile through self‐condensing vinyl copolymerization

Branched polyacrylonitrile (PAN) was prepared through a self‐condensing vinyl copolymerization of acrylonitrile and 2‐(2‐bromopropionyloxy)ethyl acrylate (BPEA). The branched architecture of the product was confirmed by NMR spectra and the average degree of branching (DB ) was estimated. Through a comparison of the intrinsic viscosity of the product with that of its linear analogue, the contraction factor g′ was calculated. It was found that the viscosity of the branched PAN was obviously lower that that of linear PAN. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Chelation properties of poly(2‐hydroxy‐4‐acryloyloxybenzophenone) resins toward some divalent metal ions

The chelation behavior of poly(2‐hydroxy‐4‐acryloyloxybenzophenone) [poly(2H4ABP) or polymer I ] obtained through the free‐radical polymerization of 2‐hydroxy‐4‐acryloyloxybenzophenone monomer and for crosslinked polymers prepared from the monomer and known amounts of the crosslinker divinylbenzene (DVB) [4 mol % of DVB for polymer II, 8 mol % of DVB for polymer III, and 16 mol 16% of DVB for polymer IV ] toward the divalent metal ions Cu²⁺, Ni²⁺, Zn²⁺, and Pb²⁺ in aqueous solution was studied by a batch equilibration technique as a function of contact time and pH. The effect of the crosslinker, DVB, was also studied. The metal‐ion uptake of the polymers was determined with atomic absorption spectroscopy, and the highest uptake was achieved at pH 7.0 for polymers I, II, III, and IV. The selectivity and binding capacity of the resins toward the investigated divalent metal ions are discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Modeling of “living” free‐radical polymerization processes. I. Batch,semibatch, and continuous tank reactors

A comprehensive mathematical model is developed for “living” free‐radical polymerization carried out in tank reactors and provides a tool for the study of process development and design issues. The model is validated using experimental data for nitroxide‐mediated styrene polymerization and atom transfer radical copolymerization of styrene and n‐butyl acrylate. Simulations show that the presence of reversible capping reactions between growing and dormant polymer chains should boost initiation efficiency when using free nitroxide in conjunction with conventional initiator and also increase the effectiveness of thermal initiation. A study shows the effects of the value of the capping equilibrium constant and capping reaction rate constants for both nitroxide‐mediated styrene polymerization (using alkoxyamine as polymer chain seeds) and atom transfer radical polymerization of n‐butyl acrylate (using methyl 2‐bromopropionate as chain extension seeds). Also the effect of introducing additional conventional initiator into atom transfer radical polymerization of n‐butyl acrylate is studied. It is found that the characteristics of long chain growth are determined by the fast exchange of radicals between growing and dormant polymer chains. Polymerization results in batch, semibatch, and a series of continuous tank reactors are analyzed. The simulations also show that a semibatch reactor is most flexible for the preparation of polymers with controlled architecture. For continuous tank reactors, the residence time distribution has a significant effect on the development of chain architecture. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1630–1662, 2002     

Synthesis and characterization of poly(vinyl chloride‐co‐vinyl acetate)‐graft‐poly[(meth)acrylates] by atom transfer radical polymerization

The graft polymerization of methyl methacrylate and butyl acrylate onto poly(vinyl chloride‐co‐vinyl acetate) with atom transfer radical polymerization (ATRP) was successfully carried out with copper(I) thiocyanate/N,N,N′,N′,N″‐pentamethyldiethylenetriamine and copper(I) chloride/2,2′‐bipyridine as catalysts in the solvent N,N‐dimethylformamide. For methyl methacrylate, a kinetic plot of ln([M]₀/[M]) (where [M]₀ is the initial monomer concentration and [M] is the monomer concentration) versus time for the graft polymerization was almost linear, and the molecular weight of the graft copolymer increased with increasing conversion, this being typical for ATRP. The formation of the graft polymer was confirmed with gel permeation chromatography, ¹H‐NMR, and Fourier transform infrared spectroscopy. The glass‐transition temperature of the copolymer increased with the concentration of methyl methacrylate. The graft copolymer was hydrolyzed, and its swelling capacity was measured. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 183–189, 2005     

Inhibition of radical polymerization in solvent‐based systems (security of solvent‐based radical polymerization of PSA‐acrylic in a plant reactor)

This article shows the influence of some chain‐transfer agents as inhibitors for acrylic solvent‐based polymerization. These chain‐transfer agents can offer significant advantages, as outlined below. The following chain‐transfer agents were studied to stop or slow down the polymerization process in the case of a runaway: n‐dodecyl mercaptan, trimethylolpropane‐trimercaptoacetate, phenothiazine, diphenylphenylen diamine, cuprum oxide, isopropanol, toluene, and carbon tetrachloride. Synthesized pressure‐sensitive adhesive based on acrylic polymers and containing 2‐ethylhexyl acrylate, methyl acrylate, and acrylic acid were used for the production of self‐adhesives with high cohesion. The polymerization was accomplished in ethyl acetate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1354–1357, 2003     

Graft polymers with macromonomers. I. Synthesis from methacrylate-terminated polystyrene

Pure graft polymers having uniform molecular weight polystyrene side chains were prepared by free radical copolymerization of methacrylate-terminated polystyrene macromonomers (MA-CROMER) with ethyl acrylate, butyl acrylate, or other suitable monomers. The MACROMER monomer was synthesized by living anionic polymerization under conditions that led to very narrow molecular weight distributions. Very effective end capping produced a material that was highly monofunctional. The graft copolymers were prepared by several techniques such as free radical solution polymerization, by aqueous suspension polymerization which produced beads, or by emulsion reactions which yielded stable latices. Polymerizations were reproducible. High conversion of the MACROMER monomer into pure graft polymers was achieved, and the product was contaminated with only a little homopolymer. The milled and molded phase-separated graft polymers had optical clarity and physical properties characteristic of polystyrene-reinforced triblock polymers. Compositions of 20-30% polystyrene were thermoplastic elastomers with good recovery. When polystyrene contents were increased, the graft products were strong, flexible thermoplastics with well defined yield strengths and increased permanent set. Copolymers of polystyrene macromers with acrylonitrile or vinyl chloride produced transparent polystyrene homopolymer-free graft polymer products having improved processing over polyacrylonitrile or poly(vinyl chloride) homopolymers.     

Ultrasonically initiated emulsion polymerization of n‐butyl acrylate

Ultrasonically initiated emulsion polymerization of n‐butyl acrylate (BA) without added initiator has been studied. The experimental results show that high conversion of BA can be reached in a short time by employing an ultrasonic irradiation technique with a high purge rate of N₂. The viscosity average molecular weight of poly(n‐butyl acrylate) (PBA) obtained reaches 5.24 × 10⁶ g mol^?1. The ultrasonically initiated emulsion polymerization is dynamic and complicated, with polymerization of monomer and degradation of polymer occurring simultaneously. An increase in ultrasound intensity leads to an increase in polymerization rate in the range of cavitation threshold and cavitation peak values. Lower monomer concentration favours enhancement of the polymerization rate. ¹H NMR, ¹³C NMR and FTIR spectroscopies reveal that there are some branches and slight crosslinking, and also carboxyl groups in PBA. Ultrasonically initiated emulsion polymerization offers a new route for the preparation of nanosized latex particles; the particle size of PBA prepared is around 50–200 nm as measured by transmission electron microscopy. © 2001 Society of Chemical Industry     

Photo‐induced emulsion polymerization of vinyl acetate in the presence of poly(oxyethylene)10 nonyl phenyl ether ammonium sulfate,an anionic emulsifier (I)

Poly(vinyl alcohol) (PVA) having a number‐average degree of polymerization of 7000 was obtained from the poly(vinyl acetate) (PVAc) having a number‐average degree of polymerization 9000, a product of photo‐induced emulsion polymerization of vinyl acetate (VAc), carried out at 0°C, using poly(oxyethylene)₁₀ nonyl phenyl ether ammonium sulfate as an anionic emulsifier. It was found that 100% conversion is always attained in the whole range of the investigation and the emulsifier plays an important role in the initiation process. The applicability of the photo‐induced emulsion polymerization system to a relatively large‐scale production was tested by using an apparatus equipped with an internal high‐pressure Hg lamp with a capacity of several hundred grams per batch under nitrogen atmosphere. It was found that both the rate of polymerization and the degree of polymerization of resulting polymers are slightly lower than those obtained from corresponding small‐scale polymerizations prepared on a high vacuum system because of the presence of oxygen. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2425–2431, 2002     

Synthesis of graft copolymers. III. Polystyrene‐g‐poly(butyl acrylate)

Polystyrene (PS) chains functionalized with pendant 1,2‐bis(trimethylsilyloxy)tetraphenylethane (TPSE) groups are used as macroinitiators to initiate the polymerization of n‐butyl acrylate (BuA) to synthesize PS‐g‐poly(BuA) (PS‐g‐PBuA) copolymers at 130°C. The TPSE groups are known to function as initers in the polymerization of several vinyl monomers. The homolytic decomposition of TPSE results in a diphenylmethyl (DPM) radical attached to the main chain and a free DPM radical. The former is responsible for the polymerization initiation and the latter momentarily stops the growth of the growing grafts by the formation of a dormant species. Unfortunately, side reactions like the combination between growing grafts take place and the polymerization can only be controlled in a limited range of conversion. The most appropriate conditions for the synthesis of PS‐g‐PBuA are reported to present their potential use as thermoplastic elastomers with relatively controlled structures. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 19–26, 2002     

Morphologies and dynamic mechanical properties of core‐shell emulsifier‐free latexes and their copolymers for P(BA/MMA)/P(MMA/BA) and P(BA/MMA)/PSt systems in the presence of AHPS

Different poly(methyl methacrylate/n‐butyl acrylate)/poly(n‐butyl acrylate/methyl methacrylate) [P(BA/MMA)/P(MMA/BA)] and poly(n‐butyl acrylate/methyl methacrylate)/polystyrene [P(BA/MMA)/PSt] core‐shell structured latexes were prepared by emulsifier‐free emulsion polymerization in the presence of hydrophilic monomer 3‐allyloxy‐2‐hydroxyl‐propanesulfonic salt (AHPS). The particle morphologies of the final latexes and dynamic mechanical properties of the copolymers from final latexes were investigated in detail. With the addition of AHPS, a latex of stable and high‐solid content (60 wt %) was prepared. The diameters of the latex particles are ～0.26 μm for the P(BA/MMA)/P(MMA/BA) system and 0.22–0.24 μm for the P(BA/MMA)/PSt system. All copolymers from the final latexes are two‐phase structure polymers, shown as two glass transition temperatures (T_gs) on dynamic mechanical analysis spectra. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3078–3084, 2002     

Preparation of acrylic/acrylate copolymeric surfactants by emulsion polymerization used in pesticide oil‐in‐water emulsions

In this work, acrylic/acrylate copolymeric surfactants, which can be used in the preparation of pesticide oil‐in‐water emulsions (EW), were synthesized by emulsion polymerization, using potassium persulfate (K₂S₂O₈) as an initiator, dodecyl mercaptan (DDM) as a chain transfer agent at the temperature range of 82–85°C. When the weight ratio of monomers was m(butyl acrylate) : m(methyl methacrylate) : m(acrylic acid) = 4 : 4 : 1.6 and the dosage of DDM was 2% (percentage of monomer mass), the prepared acrylic/acrylate copolymeric surfactants had a number‐average molecular weight of 2.5 × 10⁴ and exhibited good stability for pesticide EW. The carboxylic group distribution studies show that only the surface carboxylic groups make dispersed pesticide oil droplets more stable. The acrylic/acrylate copolymeric surfactants prepared by shot‐monomer had the most surface carboxylic group distribution (46.6%). To obtain greater surface carboxylic group distribution, maleic anhydride (MA) was used to modify the polymer system. Adding 2% MA (percentage of monomer mass) to the polymerization system, the surface carboxylic groups were increased 12% over unmodified acrylic/acrylate copolymeric surfactants. Compared with traditional pesticide EW, the avermectin EW prepared with acrylic/acrylate polymeric surfactant had much better stability. Meanwhile, its pesticide effect was similar to that of a control (1.8% abamectin emulsifiable solution). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and evaluation of sucrose‐containing polymeric hydrogels for oral drug delivery

Biodegradable and biocompatible copolymeric hydrogels based on sucrose acrylate, N‐vinyl‐2‐pyrrolidinone, and acrylic acid were designed and synthesized. Because of the growing importance of sugar‐based hydrogels as drug delivery systems, these new pH‐responsive sucrose‐containing copolymeric hydrogels were investigated for oral drug delivery. The sucrose acrylate monomer was synthesized and characterized. The copolymeric hydrogel was synthesized by free‐radical polymerization. Azobisisobutyronitrile (AIBN) was the free‐radical initiator employed and bismethyleneacrylamide (BIS) was the crosslinking agent used for hydrogel preparations. Homopolymeric vinyl pyrrolidone hydrogels were also prepared by the same technique. The hydrogels were characterized by differential scanning calorimetry, thermogravimetric analysis, and scanning electron microscopy. Equilibrium swelling studies were carried out in enzyme‐free simulated gastric and intestinal fluids (SGF and SIF, respectively). These results indicate the pH‐responsive nature of the hydrogels. The gels swelled more in SIF than in SGF. A model drug, propranolol hydrochloride (PPH), was entrapped in these gels and the in vitro release profiles were established separately in both enzyme‐free SGF and enzyme‐free SIF. The drug release was found to be faster in SIF. About 93 and 99% of the entrapped drug was released over a period of 24 h in SGF and SIF, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2597–2604, 2002