Synthesis,characterization, and utilization of itaconate‐based polymerizable surfactants for the preparation of surface‐carboxylated polystyrene latexes

Two polymerizable surfactants (surfmers), namely, monododecyl itaconate (MDDI) and monocetyl itaconate (MCI), were synthesized by reacting itaconic anhydride with 1‐dodecanol and cetyl alcohol, respectively. A series of uncrosslinked and crosslinked surface‐carboxylated latexes were prepared from styrene and styrene–divinylbenzene, respectively, using varying amounts of these two surfmers. The latexes were characterized by gravimetry, dynamic light scattering, and conductometric titration in order to obtain the conversion, particle size distribution, and concentration of surface carboxyl groups, respectively. The size of latex varied between 41–72 nm and was seen to depend inversely on the surfmer concentration. In the case of the soluble polystyrene latexes, solution ¹H NMR spectra provided conclusive evidence for surfmer incorporation into the polymer chain. Comparison of the incorporation levels determined by NMR with the surface carboxylic acid concentrations in the latexes, determined by conductometric titrations, revealed that the majority of the surfmers, as ancticipated, were present on the latex surface. The study of the stability of the latexes to varying salt concentrations clearly demonstrated that the smaller‐size latexes having higher surface carboxyl group density exhibited far improved stability when compared with the larger‐size ones having lower surface carboxyl group density. Similarly, enhanced freeze‐thaw stability was also observed for the smaller‐size latexes. MCI‐based latexes exhibited marginally improved stability compared with those prepared using MDDI, which again seems to be because of the higher surface functional group density in the former. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3257–3267, 2005     

Real‐time orientation and crystallinity measurements during the isotactic polypropylene film‐casting process

A method based on Fourier transform infrared (FTIR) transmission spectra is proposed to measure the crystallinity of isotactic polypropylene (iPP) samples. The method parameters were tuned as compared with wide‐angle X‐ray scattering measurements performed on test samples characterized by different crystallinity values obtained by solidification of thin iPP films under several cooling rates in a homemade device. The FTIR dichroic ratio measurements were adopted to measure crystalline and average Hermans' orientation factors of iPP samples obtained by film casting. The crystalline orientation measurement method was validated as compared with the birefringence measurement. The techniques were successfully used in real time during some film‐casting runs with a suitably modified FTIR system made of a spectrometer equipped with two optical guidelines and an external detector. Real‐time measurements are reported and discussed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 998–1008, 2003     

Real‐time monitoring of the ring‐opening polymerization of rac‐lactide with in situ attenuated total reflectance/Fourier transform infrared spectroscopy with conduit and diamond‐composite sensor technology

Polymerization rates were proportional to initial Sn(Oct)₂ concentration at low [Sn(Oct)₂]₀/[PrOH]₀ values, but began to level off at higher values. When [Sn(Oct)₂]₀/[PrOH]₀ was significantly greater than unity, the opposite behavior occurred. Tin(II) alkoxide concentration became limited by the initial PrOH concentration and independent of initial Sn(Oct)₂ concentration. Addition of 2‐ethylhexanoic acid caused polymerization rate retardation, without affecting molecular weight. A control polymerization was conducted in the absence of PrOH. The molecular weight of the resulting polymer was consistent with the measured water content (3.7 wt % by Karl Fisher titration) of the as‐received Sn(Oct)₂. The polymerization rate in the absence of PrOH was slow, and this suggested that water is less efficient than an alcohol in creating polymerization‐active stannyl ether bonds. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6238–6247, 2004     

New piperazine‐based polymerizable monoquaternary cationic surfactants: Synthesis,polymerization, and swelling characteristics of gels

Monoquaternary cationic polymerizable surfactants of type N‐acryloyl‐N′‐methyl‐N′‐alkyl piperazinium bromide based on piperazine heterocycle was synthesized by reacting N‐acryloyl‐N′methyl piperazine with the corresponding n‐alkyl bromide (decyl, dodecyl, tetradecyl, and hexadecyl) in anhydrous acetone at room temperature. The resulting surfactants were deliquescent to display any sharp melting points. The surface activity was studied by surface tension measurements. Due to the complex head group geometry of these surfactants, the critical micelle concentration value was high in comparison to the analogous alkyltrimethyl ammonium bromides of similar alkyl chain length. The surfactants were polymerized by micellar (in water) and isotropic (in benzene) conditions and the resulting polymers were characterized by solubility and viscosity studies. The polymers prepared in water showed higher viscosity than the ones prepared in benzene as a result of micellar aggregation in water. The reduced viscosity of the polymers in polar solvents such as methanol and dimethyl formamide (DMF) showed polyelectrolyte‐like behavior, whereas nonelectrolyte behavior was observed in chloroform. pH‐responsive hydrogels were prepared by polymerizing the surfactants in the bicontinuous phase of a microemulsion. The resulting polymers did not exhibit any definite micro/nanostructure due to cross‐polymerization of the hydrophilic oil in the bicontinuous network structure. The gels were highly responsive to changes in pH of the medium and showed high‐swelling degree in acidic media owing to the protonation of the tertiary nitrogen of the piperazine ring. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2059–2072, 2009     

PEGDA‐based luminescent polymers prepared by frontal polymerization

Frontal polymerization (FP) of poly(ethylene glycol) diacrylate (PEGDA) was carried out using benzoyl peroxide (BPO) as radical initiator. In addition, a pyrene containing monomer, 1‐pyrenebutyl acrylate (PyBuAc), was incorporated as a fluorescent probe in order to obtain luminescent materials with different chromophore contents. The resulting polymers were characterized by FT‐IR spectroscopy in the solid state and their thermal properties were determined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Moreover, the optical properties of these materials were studied by absorption and fluorescence spectroscopy. The maximum amount of the incorporated pyrene‐containing monomer into the polymer matrix was limited to 1 wt % by the polymerization process. The obtained labeled polymers poly(PEGDA‐co‐PyBuAc) exhibited a broad absorption band at 345 nm. The fluorescence spectra of these polymers exhibited mainly “monomer emission” so that no excimer emission was observed. It is possible to tune the color of the emitted light by varying the pyrene content in the samples. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2890–2897     

Polymerization kinetics of rac‐lactide initiated with alcohol/stannous octoate using in situ attenuated total reflectance‐fourier transform infrared spectroscopy: An initiator study

rac‐Lactide polymerization kinetics in THF at 72 °C were monitored in real‐time using mid‐infrared ATR‐FTIR spectroscopy, with diamond composite insertion probe and light conduit technology. Monomer concentration as a function of time was acquired using the 1240 cm^?1 resonance associated with the ? CO? O? C? stretch. Polymerizations were initiated with either n‐propanol (PrOH), ethylene glycol (EG), trimethylol propane (TMP), or pentaerythritol (PENTA) with the coinitiator stannous octoate (Sn(Oct)₂). Polymerizations were found to be reversible at high monomer conversions, with a residual monomer concentration at 72 °C (345 K) of 0.081 M. The polymerizations were internally first‐order with respect to monomer, indicating a constant concentration of propagating centers. For a typical reaction with [rac‐LA]₀ = 1.0 M, [PENTA]₀ = 1.3 × 10^?2 M, and [Sn(Oct)₂] = 2.5 × 10^?2 M, the first‐order rate constant, k_app was measured as 1.8 × 10^?4 s^?1. First‐order rate constants were determined to be independent of polymer architecture (i.e., initiator functionality) and proportional to [Sn(Oct)₂] for [Sn(Oct)₂]₀/[ROH]₀ ? 1, where [ROH]₀ represents the initial concentration of initiating hydroxyl groups. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 797–803, 2009     

Crosslinking‐induced morphology change of latex nanoparticles: A study of RAFT‐mediated polymerization in aqueous dispersed media using amphiphilic double‐brush copolymers as reactive surfactants

Amphiphilic double‐brush copolymers (DBCs) with each graft site quantitatively carrying both a hydrophilic poly(ethylene oxide) (PEO) graft and a hydrophobic polystyrene (PSt) graft are synthesized by sequential reversible addition‐fragmentation chain transfer (RAFT) polymerization and ring‐opening metathesis polymerization (ROMP). These DBCs are used as both surfactants and polyfunctional RAFT agents in the radical polymerization of St in aqueous dispersed media. Miniemulsions with narrowly dispersed St‐based nanodroplets are readily obtained after ultrasonication of the reaction mixtures. Without the presence of crosslinker, chain‐extension polymerization of St from the DBCs yields well‐defined polymeric latexes with narrow size distributions. However, with the presence of divinylbenzene (DVB) as the crosslinker, vesicular polymeric nanoparticles are formed as the major product. Such crosslinking‐induced change in morphology of the resulting latex nanomaterials may be ascribed to the increase of interfacial curvature in the heterophase systems during crosslinking polymerization. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3250–3259     

Preparation,morphology, and thermoresponsive properties of poly(N‐isopropylacrylamide)‐based copolymer microgels

In this research, thermoresponsive copolymer latex particles with an average diameter of about 200–500 nm were prepared via surfactant‐free emulsion polymerization. The thermoresponsive properties of these particles were designed by the addition of hydrophilic monomers [acrylic acid (AA) and sodium acrylate (SA)] to copolymerize with N‐isopropylacrylamide (NIPAAm). The effects of the comonomers and composition on the synthesis mechanism, kinetics, particle size, morphology, and thermoresponsive properties of the copolymer latex were also studied to determine the relationships between the synthesis conditions, the particle morphology, and the thermoresponsive properties. The results showed that the addition of hydrophilic AA or SA affected the mechanism and kinetics of polymerization. The lower critical solution temperature (LCST) of the latex copolymerized with AA rose to a higher temperature. However, because the strong hydrophilic and ionic properties of SA caused a core–shell structure, where NIPAAm was in the inner core and SA was in the outer shell, the LCST of the latex copolymerized with SA was still the same as that of pure poly(N‐isopropylacrylamide) latex. It was concluded that these submicrometer copolymer latex particles with different thermoresponsive properties could be applied in many fields. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 356–370, 2006     

Thermal and water absorption properties of cyanate ester resins modified by fluoride‐containing and silicone‐containing components

In order to enhance the moisture resistance of cyanate ester resins, modifiers containing silicon or fluorine moieties were introduced. The curing behaviors of the obtained resins, as well as thermal, water absorption, and dielectric properties of all cured polymers, were investigated in detail. Results show that properties of fillers in polymer have great influence on the thermal property and of polymer. In all cases, modifier exhibited percolation threshold at 5 wt%. Compared with pristine cyanate ester resins (CE), when the methyl phenyl silicone resin B filler was added, the cured polymer exhibited water absorption as low as 0.39% and excellent thermal oxygen stability at 300°C. The introduction of silicon H improved thermal oxidative stability at 400°C without significant compromise in processability or mechanical properties.     

Polymerization of methyl methacrylate by 2‐pyrrolidinone and n‐dodecyl mercaptan

The bulk polymerization of methyl methacrylate initiated with 2‐pyrrolidinone and n‐dodecyl mercaptan (R‐SH) has been explored. This polymerization system showed “living” characteristics; for example, the molecular weight of the resulting polymers increased with reaction time by gel permeation chromatographic analysis. Also, the polymer was characterized by Fourier transform infrared spectroscopy, ¹H NMR, and ¹³C NMR techniques. The polymer end with the iniferter structures was found. By the initial‐rate method, the polymerization rate depended on [2‐pyrrolidinone]^1.0 and [R‐SH]⁰. Combining the structure analysis and the polymerization‐rate expression, a possible mechanism was proposed. n‐Dodecyl mercaptan served dual roles—as a catalyst at low conversion and as a chain‐transfer agent at high conversion. Finally, the thermal properties were studied, and the glass‐transition temperature and thermal‐degradation temperature were, respectively, 25 and 80–100 °C higher than that of the azobisisobutyronitrile system. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3692–3702, 2002     

Adding magnetic ionic liquid monomers to the emulsion polymerization tool‐box: Towards polymer latexes and coatings with new properties

Magnetic ionic liquid monomers were synthesized and then polymerized to get magnetic polymer latexes and films. First, a series of 1‐vinyl‐3‐dodecyl‐imidazolium monomers having metal halides counter‐anions such as FeCl₃Br^?, CoCl₂Br^?, and MnCl₂Br^? were synthesized. These ionic liquid monomers were first homopolymerized to lead to magnetic poly(ionic liquids) and characterized. Secondly, magnetic latexes were synthesized by using the magnetic ionic liquids as surfmers (surfactant + monomer) in the emulsion polymerization of methyl methacrylate/n‐butyl acrylate. It was found that the powders obtained by freeze‐drying the latexes presented a paramagnetic behavior with weak antiferromagnetic interactions between the adjacent metal ions. Although the ratio of magnetic ionic liquid/monomer was only 2% these poly(methyl methacrylate‐co‐butyl acrylate) powders and latexes responded to a magnetic field due to the surfmer paramagnetic nature. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1145–1152     

High‐density polyethylene layered silicate nanocomposites: Effect of mechanical stretching on the crystal‐to‐crystal transformations,morphology, and extent of exfoliation

High‐density polyethylene/clay nanocomposites were elongated until breakage to investigate the effect of the mechanical stretching on the crystal‐to‐crystal transformations and their morphology. Crystalline transformations of the polymer matrix were studied via Fourier transform infrared spectroscopy, differential scanning calorimetry, and X‐ray diffraction measurements. It was concluded that the stress‐induced crystal‐to‐crystal transformations from orthorhombic structures to monoclinic and pseudohexagonal structures as well as the back‐transformation during relaxation were hindered by the presence of the clay. X‐ray diffraction studies on stretched samples showed that the mechanical stretching led from an intercalated structure to an almost exfoliated structure. These findings agreed with scanning electron micrographs, in which the beneficial effect of stretching on the exfoliation of the clay was evident. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 914–924, 2006     

RAFT‐mediated batch emulsion polymerization of styrene using poly[N‐(4‐vinylbenzyl)‐N,N‐dibutylamine hydrochloride] trithiocarbonate as both surfactant and macro‐RAFT agent

Poly[N‐(4‐vinylbenzyl)‐N,N‐dibutylamine hydrochloride] trithiocarbonate, which contains the reactive trithiocarbonate group and the appending surface‐active groups, is used as both surfactant and macromolecular reversible addition‐fragmentation chain transfer (macro‐RAFT) agent in batch emulsion polymerization of styrene. Under the conditions at high monomer content of ～20 wt % and with the molecular weight of the macro‐RAFT agent ranging from 4.0 to 15.0 kg/mol, well‐controlled batch emulsion RAFT polymerization initiated by the hydrophilic 2‐2′‐azobis(2‐methylpropionamidine) dihydrochloride is achieved. The polymerization leads to formation of nano‐sized colloids of the poly[N‐(4‐vinylbenzyl)‐N,N‐dibutylamine hydrochloride]‐b‐ polystyrene‐b‐poly[N‐(4‐vinylbenzyl)‐N,N‐dibutylamine hydrochloride] triblock copolymer. The colloids generally have core‐shell structure, in which the hydrophilic block forms the shell and the hydrophobic block forms the core. The molecular weight of the triblock copolymer linearly increases with increase in the monomer conversion, and the values are well‐consistent with the theoretical ones. The molecular weight polydispersity index of the triblock copolymer is below 1.2 at most cases of polymerization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Emulsifier‐free,organotellurium‐mediated living radical emulsion polymerization (emulsion TERP): Effect of monomer hydrophilicity

Emulsifier‐free, organotellurium‐mediated living radical emulsion polymerizations (emulsion TERPs) of methyl methacrylate (MMA) and n‐butyl methacrylate (BMA) with dimethyl ditelluride were carried out at two different stirring rates (220 rpm and 1000 rpm). In the emulsion TERP of MMA as a hydrophilic monomer, the molecular weight distribution (MWD) controls with both stirring rates were good with high polymerization rate (100% conversion at 1.5 h). On the other hand, in the emulsion TERP of BMA as a hydrophobic monomer, at 220 rpm the polymerization rate was much slow (～50% conversion at 22 h) and the MWD control was bad, but at 1000 rpm the polymerization was completed within 7 h and MWD control was good. These results suggest that monomer transportation from droplets to polymerizing particles via aqueous medium is important for good MWD control and steady polymerization in the emulsion TERP. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Ring‐opening polymerization of L‐lactide using half‐titanocene complexes of the ATiCl2Nu type: Synthesis,characterization, and thermal properties

Various half‐titanocene complexes of the ATiCl₂Nu type, where A is the pentamethylcyclopentadienyl (Cp*) or indenyl (Ind) group and Nu a nucleophile (ethoxy group or chloride), were used for the polymerization of L ‐lactide, LLA. In the cases where Nu is an ethoxy group, a 5% excess of ATiCl₃ was used to accelerate the polymerization reaction. These systems were proven to be very efficient initiators for the ring‐opening polymerization (ROP) of LLA in toluene at 130 °C. Kinetic studies revealed that in most cases the polymerization yield was quantitative and the molecular weight increased linearly with time, leading to well‐defined PLLA with narrow molecular weight distributions (M_w/M_n ≤ 1.1). LLA was also polymerized by the in situ formation of the initiating system after mixing IndTiCl₃, benzyl alcohol, BzOH, and NEt₃. The thermal properties of the produced polymers were examined by differential scanning calorimetry and thermogravimetric analysis. The activation energy of the thermal decomposition was calculated by the Ozawa–Flynn–Wall and Kissinger methods. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis,characterization, and thermal properties of dendrimer‐star,block‐comb copolymers by ring‐opening polymerization and atom transfer radical polymerization

Novel and well‐defined dendrimer‐star, block‐comb polymers were successfully achieved by the combination of living ring‐opening polymerization and atom transfer radical polymerization on the basis of a dendrimer polyester. Star‐shaped dendrimer poly(?‐caprolactone)s were synthesized by the bulk polymerization of ?‐caprolactone with a dendrimer initiator and tin 2‐ethylhexanoate as a catalyst. The molecular weights of the dendrimer poly(?‐caprolactone)s increased linearly with an increase in the monomer. The dendrimer poly(?‐caprolactone)s were converted into macroinitiators via esterification with 2‐bromopropionyl bromide. The star‐block copolymer dendrimer poly(?‐caprolactone)‐block‐poly(2‐hydroxyethyl methacrylate) was obtained by the atom transfer radical polymerization of 2‐hydroxyethyl methacrylate. The molecular weights of these copolymers were adjusted by the variation of the monomer conversion. Then, dendrimer‐star, block‐comb copolymers were prepared with poly(L ‐lactide) blocks grafted from poly(2‐hydroxyethyl methacrylate) blocks by the ring‐opening polymerization of L ‐lactide. The unique and well‐defined structure of these copolymers presented thermal properties that were different from those of linear poly(?‐caprolactone). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6575–6586, 2006     

Sterically stabilized emulsion polymerization of styrene: Pseudo‐semicontinuous approach

The sterically stabilized emulsion polymerization of styrene initiated by a water‐soluble initiator at different temperatures has been investigated. The rate of polymerization (R_p) versus conversion curve shows the two non‐stationary‐rate intervals typical for the polymerization proceeding under non‐stationary‐state conditions. The shape of the R_p versus conversion curve results from two opposite effects—the increased number of particles and the decreased monomer concentration at reaction loci as the polymerization advances. At elevated temperatures the monomer emulsion equilibrates to a two‐phase or three‐phase system. The upper phase is transparent (monomer), and the lower one is blue colored, typical for microemulsion. After stirring such a multiphase system and initiation of polymerization, the initial coarse polymer emulsion was formed. The average size of monomer/polymer particles strongly decreased up to about 40% conversion and then leveled off. The initial large particles are assumed to be highly monomer‐swollen particles formed by the heteroagglomeration of unstable polymer particles and monomer droplets. The size of the “highly monomer” swollen particles continuously decreases with conversion, and they merge with the growing particles at about 40–50% conversion. The monomer droplets and/or large highly monomer‐swollen polymer particles also serve as a reservoir of monomer and emulsifier. The continuous release of nonionic (hydrophobic) emulsifier from the monomer phase increases the colloidal stability of primary particles and the number of polymer particles, that is, the particle nucleation is shifted to the higher conversion region. Variations of the square and cube of the mean droplet radius with aging time indicate that neither the coalescence nor the Ostwald ripening is the main driving force for the droplet instability. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 804–820, 2003