Plasma‐induced graft polymerization of acrylic acid onto poly(ethylene terephthalate) films

The graft polymerization of acrylic acid was carried out onto poly(ethylene terephthalate) films that had been pretreated with argon plasma and subsequently exposed to oxygen to create peroxides. The influence of synthesis conditions, such as plasma treatment time, plasma power, monomer concentration, temperature, and the presence of Mohr's salt, on the degree of grafting was investigated. The observed initial increase in grafting with monomer concentration accelerated at about 20% monomer. The grafting reached a maximum at 40% monomer and subsequently decreased with further increases in monomer concentration. The reaction temperature had a pronounced effect on the degree of grafting. The initial rate of grafting increased with increasing temperature, but the degree of grafting showed a maximum at 50°C. The activation energy of the grafting obtained from an Arrhenius plot was 29.1 kJ/mol. The addition of Mohr's salt to the reaction medium not only led to a homopolymer‐free grafting reaction but also diminished the degree of grafting. The degree of grafting increased with increasing plasma power and plasma treatment time. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2993–3001, 2001     

Synthesis of new free‐radical initiators for polymerization

Synthesis and properties of new initiating systems formed from commercially available ketones, glycols, and hydrogen peroxide (60%) are presented. In preparation of free radical initiators methyl ethyl ketone, which was oxidized by hydrogen peroxide, was used. Reaction was carried out in etanodiol or 1,4‐butanodiol as diluent. The obtained initiators with cobalt octoate as a promotor were applied for crosslinking of the commercially available unsaturated polyester resin. Properties of the resin were compared with those obtained while it was hardened by the typical curing system containing methyl ethyl ketone hydroperoxide and cobalt octoate. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2238–2243, 2003     

Kinetics and crystallization in pH‐sensitive free‐radical crosslinking polymerization of acrylic acid

Free‐radical crosslinking polymerization and crystallization of acrylic acid (AAc) were investigated by shear storage modulus (G′) measurements in pH 2, as well as in pH 6 and pH 10, by varying the molar ratio of crosslinking agent (N,N′‐methylene bis‐acrylamide; MBAAm) to AAc (0.583 × 10^?3, 1.169 × 10^?3, 1.753 × 10^?3, and 2.338 × 10^?3). Our results showed that the pre‐gelation time was the same at pH 2, regardless of the concentration of MBAAm. The propagation time was determined by the initial feed concentration of AAc, and the length of the linear curve in the propagation was proportional to the concentration of MBAAm. The Avrami exponent (n), as an indicative of growing pattern of an infinite molecule, in the crystallization was increased in proportional to the concentration of MBAAm, and generally low at pH 2. In the deceleration phase, n was observed near 1.0 throughout the all specimens. These results indicated that (1) the length of the pre‐gelation period was determined by the ionization of AAc (or pH), (2) the polymerization rate of AAc was not affected by the concentration of MBAAm, and (3) the inhomogeneity of hydrogel was determined by the growing pattern of infinite molecule in propagation phase. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42195.     

Controlled radical polymerization of p-(iodomethyl)styrene—a route to branched and star-like structures

p-(Iodomethyl)styrene was polymerized under the action of a radical initiator (AIBN). The polymerization proceeds with degenerative chain transfer and leads to well defined branched polymers with functional primary and secondary iodomethyl groups as revealed by NMR studies. The obtained polymer can be further used as macroinitiator for radical polymerization of styrene. This polymerization proceeds in controlled way to polystyrene star polymers with reactive groups at the end of their arms. The characterization of branched and star structures was performed by NMR and GPC with absolute molar mass detection (MALLS).     

Soil polymer conditioner based on montmorillonite‐poly(acrylic acid) composites

The constant deterioration of the soil as a result of natural and anthropogenic processes produces decrease of soil fertility and agricultural production, increase in the cost of food, desertification, and loss of water resources. The objective of this work was to develop a hybrid composite that structural and functionally mimics the humified structure of soils for the development of remediation strategies based on geotransformation of degraded soils. For that, two different strategies for the modification of clay surface were evaluated: (i) covalent linking using trichlorovinylsilane and (ii) electrostatic interaction using N‐vinylbenzyl‐N‐triethyl ammonium chloride. Later, modified clay was characterized and used as crosslinking agent during the free‐radical polymerization of acrylic acid. Particulate nanostructured polymers were characterized and their water absorption capacity, cationic exchange capacity, and ionic retention capacity were determined. Results showed that clay‐poly(acrylic acid) composites can be obtained by described methodology. In addition, materials with 60 and 80% w/w of modified MMT were obtained with particulate shape, high water absorption capacity (273%–568%), high cationic exchange capacity (124–666 meq+/100 g) and high ionic retention capacity (108–194 and 263–313 meq/100 g for major and minor elements, respectively). Finally, it was concluded that synthesized materials mimic structural and functionally the humified structure of soils. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46211.     

Inhibition of calcium oxalate monohydrate by poly(acrylic acid)s with different end groups

Water‐soluble low molecular weight polymers are known to affect the crystal habit of scale‐forming minerals and their rates of deposition. Poly(acrylic acid) (PAA) and poly(maleic acid) are commonly used to control scale formation in sugar mill evaporators. Calcium oxalate (both mono‐ and dihydrate) forms the bulk of the hard intractable scale found in Australian sugar mills, causing efficiency losses of significant economic importance. In this work, the formation of calcium oxalate monohydrate in a synthetic juice solution was investigated in the presence of PAAs of varying molecular weights and end‐group functionality and a strong dependency on both of these factors was observed. Terminal functionality was controlled using three chain‐transfer agents (CTA): thioethanol, thioglycolic acid, and dodecanthiol. Effectiveness of inhibition varied with CTA in the order thioethanol ～ thioglycolic acid > dodecanthiol for all molecular weights. This suggests that polymer end groups play a role in scale inhibition. The polymers that were prepared with dodecanthiol accelerated rather than inhibited calcium oxalate formation, implying a different mode of action on calcium oxalate crystallization. Consistent with previous reports for other scales, the calcium oxalate inhibition tests show optimum effectiveness for PAAs of molecular weight 2000–4000. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2035–2041, 2004     

Amphiphilic styrene–acrylic acid copolymers from the free‐radical retrograde‐precipitation polymerization (FRRPP) process

The free‐radical retrograde‐precipitation polymerization (or FRRPP) process, a free‐radical polymerization that occurs above the lower critical solution temperature (LCST), was extended to copolymer formation. Control over the rate of polymerization and entrapment of polymer radicals in the FRRPP process was used to generate tapered styrene–acrylic acid block copolymers. To show the effectiveness of the FRRPP process, the same procedure was used with solvents that are not LCST‐based precipitants for the polymer. Kinetic data show substantial chain termination in non‐FRRPP copolymerization systems. Molecular weight information also shows propagation control in the FRRPP system. Solubilization and emulsification studies also indicate the capability of the FRRPP system in generating a much higher proportion of amphiphilic tapered block copolymers in the solid product. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 426–431, 2003     

用电子转移活化再生原子转移自由基聚合制备含氟丙烯酸酯共聚物及其表征

在水分散介质中,以非离子乳化剂Tween-80和十二烷基磺酸钠作为复合乳化剂,通过电子转移活化再生原子转移自由基聚合,采用"ab二次引发"乳液聚合法制备了含氟丙烯酸酯三元共聚物,用傅里叶变换红外光谱、拉曼光谱、核磁共振波谱及凝胶渗透色谱等对其结构、组成和相对分子质量及其分布进行了表征。结果表明,含氟丙烯酸酯聚合物的分子结构及组成可控,转化率高达95%,相对分子质量分布较窄。优选憎水性配体和惰性乳化剂可提高反应的可控性。     

Free‐radical retrograde‐precipitation copolymerization of vinyl acetate and acrylic acid

Free‐radical chain polymerization kinetics of vinyl acetate (VA) and acrylic acid (AA) exhibit some unusual control features. The VA radicals have a high rate of chain transfer leading to relatively sluggish propagation rates. Polymerization of AA, however, is prone to autoacceleration behavior in bulk, solution, and precipitating media. Thus, conventional statistical copolymerization of VA and AA would result in the preferential formation of high AA content copolymer. However, when the reaction medium is chosen in such a way that the copolymer precipitates above the lower critical solution temperature (LCST), propagation control and even monomer sequence control are obtained. Under these conditions, when the VA charge is much greater than AA, a tapered block copolymer (VA‐t‐AA) is obtained. We report a single stage polymerization process for the synthesis of such materials. The presence of VA‐t‐AA products is verified by emulsification, solubility, fractionation, size exclusion chromatography, NMR, and thermal analyses. In addition, propagation control can virtually eliminate formation of bimodal MWD and random/homopolymer materials that are associated with various chain transfer mechanisms in conventional polymerization routes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Uniform star‐polystyrene nanoparticles prepared by emulsion atom transfer radical polymerization

Pentaerythritol (PT) was converted into four‐arm initiator pentaerythritol tetrakis(2‐chloropropionyl) (PT‐Cl) via reaction with 2‐chloropropionyl chloride. Uniform (monodisperse) star‐polystyrene nanoparticles were prepared by emulsion atom transfer radical polymerization of styrene, using PT‐Cl/CuCl/bpy (bpy is 2,2′‐dipyridyl) as the initiating system. The structures of PT‐Cl and polymer were characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance. The morphology, size and size distribution of the star‐polystyrene nanoparticles were characterized by transmission electron microscopy, atomic force microscopy and photon correlation spectroscopy. It was found that the average diameters of star‐polystyrene nanoparticles were smaller than 100 nm (30–90 nm) and monodisperse; moreover, the particle size could be controlled by the monomer/initiator ratio and the surfactant concentration. The average hydrodynamic diameter (D_h) of the nanoparticles increased gradually on increasing the ratio of styrene to PT‐Cl and decreased on enhancing the surfactant concentration or increasing the catalyst concentration. Copyright © 2011 Society of Chemical Industry     

Effect of acrylic acid neutralization on ‘livingness’ of poly[styrene‐ran‐(acrylic acid)] macro‐initiators for nitroxide‐mediated polymerization of styrene

BACKGROUND: The effect of acrylic acid neutralization on the degradation of alkoxyamine initiators for nitroxide‐mediated polymerization (NMP) was studied using styrene/acrylic acid and styrene/sodium acrylate random copolymers (20 mol% initial acrylate feed concentration) as macro‐initiators. The random copolymers were re‐initiated with fresh styrene in 1,4‐dioxane at 110 °C at SG1 mediator/BlocBuilder^® unimolecular initiator ratios of 5 and 10 mol%. RESULTS: The value of k_pK (k_p = propagation rate constant, K = equilibrium constant) was not significantly different for styrene/acrylic acid and styrene/sodium acrylate compositions at 110 °C (k_pK = 2.4 × 10^?6–4.6 × 10^?6 s^?1) and agreed closely with that for styrene homopolymerization at the same conditions (k_pK = 2.7 × 10^?6–3.0 × 10^?6 s^?1). All random copolymers had monomodal, narrow molecular weight distributions (polydispersity index M?_w/M?_n = 1.10–1.22) with similar number‐average molecular weights M?_n = 19.3–22.1 kg mol^?1. Re‐initiation of styrene/acrylic acid random copolymers with styrene resulted in block copolymers with broader molecular weight distributions (M?_w/M?_n = 1.37–2.04) compared to chains re‐initiated by styrene/sodium acrylate random copolymers (M?_w/M?_n = 1.33). CONCLUSIONS: Acrylic acid degradation of the alkoxyamines was prevented by neutralization of acrylic acid and allowed more SG1‐terminated chains to re‐initiate the polymerization of a second styrenic block by NMP. Copyright © 2008 Society of Chemical Industry     

Temperature distribution effects during polymerization of methacrylate‐based monoliths

Monolithic stationary phases are becoming increasingly important in the field of liquid chromatography. Methacrylate‐based monoliths are produced via free‐radical bulk polymerization. The preparation of large‐volume monoliths is a major problem because the intensive heat released during polymerization causes distortion of the porous monolithic structure. This work presents experimental measurements of temperature distributions during polymerization in moulds of different sizes and at various experimental conditions. A mathematical model for the prediction of temporal and spatial temperature distribution during the polymerization of methacrylate‐based monolithic columns is introduced. The polymerization is described by an unsteady‐state heat conduction equation with the generation of heat related to the general kinetics of polymerization. Predictions from the mathematical model are in good agreement with the experimental measurements at different experimental conditions. A method for construction of large‐volume monolithic columns is presented and an attempt is made to adopt the developed mathematical model in annular geometry. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2326–2334, 2003     

Synthesis and properties of acrylate‐acrylic acid‐acrylate triblock copolymers with gemini structure by RAFT polymerization

A class of gemini structure block copolymers with a trithiocarbonate ester spacer group had been synthesized with S, S′‐bis (R, R′‐dimethylacetic acid) trithiocarbonate as reversible addition fragmentation chain transfer agents and acrylic acid as the second monomer. These triblock copolymers were characterized by ¹H NMR spectroscopy, gel permeation chromatography in terms of their compositions, molecular weights and behaviour at the air–water interface. The results showed that the weight‐average molecular weight was larger than theoretical molecular as the acrylate side chain increased. The polymer neutralized by sodium hydroxide solution had low critical micelle concentration which was <10^?2 mol L^?1 in water. TEM and DLS showed that it formed a special micelle structure with large pore structure which might lead to low surface tension and critical micelle concentration in water. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43017.     

Thermosensitive copolymer synthesized by controlled living radical polymerization: Phase behavior of diblock copolymers of poly(N‐isopropyl acrylamide) families

In this study, we prepared a series of thermosensitive polymers with low polydispersity index (PDI) values by nitroxide‐mediated controlled radical polymerization (NMRP) with 2,2,6,6‐tetramethyl‐1‐piperdinyloxy nitroxide (TEMPO) as a stable nitroxide‐free radical. Poly(N‐isopropyl acrylamide) (PNIPAAm)‐block‐poly(N‐tert‐butyl acrylamide) (PNTBA) was successfully synthesized, first, through polymerization with N‐isopropyl acrylamide to obtain the reactive polymer PNIPAAm‐TEMPO and, second, through polymerization by the addition of N‐tert‐butyl acrylamide (NTBA). The added molar fraction of NTBA during the second polymerization was adjusted accordingly to obtain the final polymerization product, a thermosensitive polymer (PNIPAAm‐block‐PNTBA), which had a targeted lower critical solution temperature (LCST). The result shows that the synthesis method used in this study effectively controlled the formation of the polymer to obtain a low PDI. The thermosensitive block copolymer, PNIPAAm‐b‐PNTBA (molar ratio = 9:1), with LCSTs in the range 27.7–39.8°C, was obtained through controlled living radical polymerization with PNIPAAm–TEMPO. Specifically, the 5 wt % aqueous solution of PNIPAAm‐b‐PNTBA (molar ratio = 9:1) had an LCST of 37.4°C; this was close to body temperature, 37°C. The 5 wt % aqueous solution of PNIPAAm‐b‐PNTBA (molar ratio = 9:1) showed potential for use in biomedical applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43224.     

Characterization of acrylic acid‐grafted PP membranes prepared by plasma‐induced graft polymerization

Acrylic acid (AA)‐g‐polypropylene (PP) membranes were prepared by grafting AA on to a microporous PP membrane via plasma‐induced graft polymerization. The grafting of AA to the PP membrane was investigated using Fourier transform infrared spectroscopy (FTIR). Pore‐filling of the membranes was confirmed by field emission‐scanning electron microscopy (FESEM) and energy dispersing X‐ray (EDX). Ion exchange capacity (IEC), membrane electric resistance, transport number and water content were measured and analyzed as a function of grafting reaction time. The prepared AA‐g‐PP membranes showed moderate electrochemical properties as a cation‐exchange membrane. In particular, membranes with a degree of grafting of 155% showed good electrical properties, with an IEC of 2.77 mmol/g dry membrane, an electric resistance of 0.4 Ω cm² and a transport number of 0.96. Chronopotentiometric measurements indicated that AA‐g‐PP membranes, with a high IEC had a sufficient conducting region in the membrane. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Two‐stage grafting onto polyethylene fiber by radiation‐induced graft polymerization and atom transfer radical polymerization

Two‐stage graft polymerization onto polyethylene (PE) fiber was demonstrated. The graft side chain was formed by radiation‐induced graft polymerization. A PE fiber was irradiated with an electron beam and immersed in a vinyl monomer solution. The terminal of the formed graft chain was halogenated using N‐bromosuccinimide. The halogenated graft chain was then extended by atom transfer radical polymerization to obtain block‐copolymer grafted PE fibers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Novel comb‐structured‐polymer‐grafted carbon black by surface‐initiated atom transfer radical polymerization and ring‐opening polymerization

Novel comb‐structured‐polymer‐grafted carbon black (CB) was synthesized with a combination of surface‐initiated atom transfer radical polymerization and ring‐opening polymerization. First, poly(2‐hydroxyethyl methacrylate) (PHEMA) was grafted onto the CB surface by surface‐initiated atom transfer radical polymerization. The prepared CB‐g‐PHEMA contained 35.6–71.8% PHEMA, with the percentage depending on the molar ratio of the reagents and the reaction temperature. Then, with PHEMA in CB‐g‐PHEMA as the macroinitiator, poly(?‐caprolactone) (PCL) was grown from the CB‐g‐PHEMA surface by ring‐opening polymerization in the presence of stannous octoate. CB‐g‐PHEMA and CB‐g‐(PHEMA‐g‐PCL) were characterized with Fourier transform infrared, ¹H‐NMR, thermogravimetric analysis, dynamic light scattering, and transmission electron microscopy. The resultant grafted CB had a shell of PHEMA‐g‐PCL. On the whole, the CB nanoparticles were oriented in dendritic lamellae formed by these shells. This hopefully will result in applications in gas sensor materials and nanoparticle patterns. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Kinetics of RAFT emulsion polymerization of styrene mediated by oligo(acrylic acid‐b‐styrene) trithiocarbonate

The kinetics of ab initio reversible addition‐fragmentation chain transfer (RAFT) emulsion polymerization of styrene using oligo(acrylic acid‐b‐styrene) trithiocarbonate as both polymerization mediator and surfactant were systematically investigated. The initiator concentration was set much lower than that in the conventional emulsion polymerization to significantly suppress the irreversible termination reaction. It was found that decreased rapidly but the nucleation efficiency of micelles increased with the decrease of the initiator concentrations due to the significant radical exit. The particle number ( ) did not follow the classic Smith–Eward equation but was proportional to [I]^?0.4[S]^0.7. It was suggested that RAFT emulsion polymerization could be fast enough for commercial use even at extremely low initiator concentrations and low macro‐RAFT agent concentrations due to the higher particle nucleation efficiency at lower initiator concentration. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2126–2134, 2016     

Preparation and characterization of polyaniline N‐grafted with poly(ethyl acrylate) synthesized via atom transfer radical polymerization

Polyaniline (PANI) N‐grafted with poly(ethyl acrylate) (PEA) was synthesized by the grafting of bromo‐terminated poly (ethyl acrylate) (PEA‐Br) onto the leucoemeraldine form of PANI. PEA‐Br was synthesized by the atom transfer radical polymerization of ethyl acrylate in the presence of methyl‐2‐bromopropionate and copper(I) chloride/bipyridine as the initiator and catalyst systems, respectively. The leucoemeraldine form of PANI was deprotonated by butyl lithium and then reacted with PEA‐Br to prepare PEA‐g‐PANI graft copolymers containing different amounts of PEA via an N‐grafting reaction. The graft copolymers were characterized by Fourier transform infrared spectroscopy, elemental analysis, and thermogravimetric analysis. Solubility testing showed that the solubility of PANI in chloroform was increased by the grafting of PEA onto PANI. The morphology of the PEA‐g‐PANI graft copolymer films was observed by scanning electron microscopy to be homogeneous. The electrical conductivity of the graft copolymers was measured by the four‐probe method. The results show that the conductivity of the PANI decreased significantly with increasing grafting density of PEA onto the PANI backbone up to 7 wt % and then remained almost constant with further increases in the grafting percentage of PEA. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Environmentally responsive amphiphilic cationic block copolymers synthesized by 2,2,6,6‐Tetramethylpiperidinyloxy mediated living free‐radical polymerization

Polychloromethylstyrene (PCMS)‐block‐polystyrene (PS) copolymers were prepared by controlled free‐radical polymerization in the presence of 2,2,6,6‐tetramethylpiperidinooxy and 2,2′‐azobisisobutyronitrile (AIBN) initiator. The PCMS‐b‐PS copolymers had narrow molecular weight distributions, and the block lengths were controlled by the reaction time and the molar ratios of chloromethylstyrene/AIBN and styrene/PCMS macroinitiator. The block copolymers were further quaternized with triethylamine. The amphiphilic cationic block copolymers formed colloidal particles; the effects of the pH value, salt concentration, and solvent polarity on the particle size were investigated with a dynamic light scattering analyzer. The average colloid size increased with increasing pH value and salt concentration. This implied that the colloid formed a protonated hydrophilic shell and hydrophobic styrene core in water. Furthermore, with the addition of tetrahydrofuran to the aqueous solution, the styrene segments in the core could be inverted to the outside of the colloid. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013