Surface properties of some styrene/vinyl pyridine diblock polymers adsorbed on rutile

Inverse gas chromatography (IGC) has been applied for the surface characterization of styrene-4-vinyl pyridine (S-4VP) diblock polymers of varying composition and of two rutile pigments. The latter were used as adsorbents for the polymers. Dispersion surface energies and acid-base interaction parameters were obtained from the IGC data. These show that the adsorbed layers form interphases where the local composition varies with the mass of adsorbed polymer and also with the acid-base interaction between rutile and the polymer. The results may be rationalized by suggesting that the more basic 4VP moiety preferentially orients to the acidic rutile surfaces, leaving surface compositions enriched in the less basic polystyrene (PS), which also has a lower surface energy. The effect was more pronounced when the strength of acid-base forces at the interface was increased. The experimental findings also permit the calculation of thicknesses for the adsorbed interphases. These were found to be in the range 30-90 nm, depending on the mass of adsorbed polymer and on its acid-base interaction with the adsorbing pigment surface.     

Characterization of styrene/methacrylic acid copolymers by 2D-NMR spectroscopy

Styrene/methacrylic acid copolymers were prepared by free-radical photopolymerization using the uranyl nitrate ion as the initiator. The copolymer composition was determined from ¹H-NMR spectroscopy. The comonomer reactivity ratios determined using Kelen Tudos and nonlinear error in variable methods (EVM) are r_m = 0.61 ± 0.05 and r_s = 0.14± 0.07. The broad and overlapping ¹H-NMR spectrum was assigned using the help of 2D TOCSY and NOESY experiments. These methods were used to ascertain the various geminal, vicinal, and spatial couplings between the protons. The methyl and methine protons also show configurational and compositional sensitivity. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2444–2453, 2001     

Preparation of block copolymers of styrene and methacrylic acid

A range of block copolymers of styrene and methacrylic acid has been prepared by the suspension method involving migration of a growing radical across a phase boundary. The way in which copolymer composition varies with change in the amount of the two monomers in the reaction mixture has been studied, and explanations are suggested to account for these variations. Two methods, involving calculation from solubility data and thermogravimetric analysis respectively, have been used to give an estimate of the length and composition of the blocks.     

Simulation of kinetic analysis on terpolymerization of styrene/butyl methacrylate/methacrylic acid system

The simultaneous differential equations which connected the copolymerization kinetics of the component reaction in the multi-copolymerization system with the changing rate of the concentration of each monomer and radical, the concentration and the molecular weight of the polymer obtained are analysed in a number of ways. The distribution of the components and the degree of polymerization are also simulated. The styrene/butyl methacrylate/methacrylic acid terpolymerization system, using carbon tetrachloride as solvent and benzoyl peroxide as initiator, was chosen. The simulation model which satisfied the experimental values of the concentration of the multiple components in the system, the composition and molecular weight distribution and the number of chlorine atoms introduced into the copolymer ends is established. When the time interval changed, the effects on the distribution of the composition in copolymers and the distribution of the degree of polymerization were also calculated.     

Mechanical and rheological properties of styrene/acrylic gradient polymers

A butyl acrylate monomer with a small amount of photosensitizer was diffused into a slightly crosslinked polystyrene matrix. After a certain swelling time, the diffusion gradient was either fixed (by rapid photopolymerization in situ) to form a gradient polymer or changed to form an interpenetrating polymer network (IPN), once thermodynamic equilibrium was achieved. Chemical compositions were determined by FTIR. Mechanical and rheological measurements were performed using a universal testing machine and dynamic rheometer, respectively. Impact properties were evaluated with a Falling Dart Impact Tester. Compared to the IPN materials, the gradient polymers exhibit higher moduli, considerable strain, and similar impact resistance. They are also able to retain plastic properties at higher temperatures. Differences in chemical structure of equivalent layers for gradient and IPN polymers yield such differences in properties. © 1995 John Wiley & Sons, Inc.     

The preparation of block copolymers of styrene and methacrylic acid

A new method of preparing block copolymers of styrene and methacrylic acid is described. It is based upon use of the anionically initiated “living chain” method to prepare block copolymers of styrene and methyl methacrylate, with subsequent hydrolysis of the methyl methacrylate block to methacrylic acid.     

Emulsifier‐free emulsion copolymerization of styrene with methacrylic acid

The study on batch emulsifier‐free emulsion copolymerization of styrene with methacrylic acid was conducted. The copolymerization process was followed by gravimetry, infrared, and transmission electron microscopy. The copolymerization mechanism differs from that of styrene with acrylic acid. The effect of solid content on particle size was examined, and it was found that the particle size was increased as the solid content was increased. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1747–1751, 2003     

Optical anisotropy and non-linear optical properties of azobenzene methacrylic polymers

Photoinduced optical anisotropy has been studied in several methacrylic copolymers, either amorphous or liquid crystalline, with cyano azobenzene chromophores in the side chain. Illumination with linearly polarised 488 nm light gives rise to high and stable values of birefringence and dichroism, mainly in liquid crystalline films. Both dichroism and birefringence decrease with the azo content in the copolymer series while some increase can be achieved by the incorporation of biphenyl molecules to the copolymers. Photoinduced anisotropy disappears above the glass transition temperature in amorphous polymers, whereas it increases in liquid crystalline polymers (LCP) due to a thermotropic self-organisation.The non-linear optical (NLO) properties of the films have been studied by second harmonic generation (SHG) measurements. The intensity of the harmonic signal from in situ corona poled polymeric films has been measured. The effect of 488 nm light irradiation on the azo chromophores orientation and consequently on the NLO response of the films was investigated at different temperatures. The intensity and thermal stability of the second harmonic signals obtained after the two different (thermal and photoassisted) corona poling processes have been compared.     

Thickening of butyl acrylate/styrene/2-hydroxyethyl methacrylate/acrylic acid lattices with dispersion of crosslinked ethyl acrylate/methacrylic acid copolymer

Thickening of lattices of styrene–acrylic copolymers containing a small amount of acrylic acid and various amounts of 2-hydroxyethyl methacrylate (HEMA) with alkali-swellable dispersion of crosslinked ethyl acrylate/methacrylic acid copolymer has been studied using capillary viscometry and dynamic and steady shear measurements. The higher the amount of HEMA incorporated into the latex copolymers, the stronger the thickening effect is. A comparison of flow behavior of thickened systems with those of neat lattices confirmed a significant influence of the effective volume fraction of alkalinized swollen latex particles on the thickening process. Under these conditions, to obtain the same rheological properties, the necessary amount of thickener was lower for the latex copolymers with higher amounts of HEMA because a part of the thickener volume fraction was replaced by an increased volume fraction of swollen latex particles. These findings indicate weakly interacting dispersion systems without strong compression of particle domains.     

Preparation and surface properties of fluorine-containing diblock copolymers

Two series of semifluorinated fluorocarbon diblock copolymer poly(butyl methacrylate-co-perfluoroalkyl acrylate) have been synthesized by atom transfer radical polymerization (ATRP). The ¹H NMR, F-EA, GPC and FTIR were used to characterize copolymer structure. Contact angle measurements on the thin polymer films showed low critical surface tensions and low dispersion force contributions to the surface energy, which indicated the presence of the fluorinated block at the surface. The results showed that the water- and oil-repellency increased with the fluorine content in the diblock copolymers. After annealing at different temperatures or different times, the water- and oil-repellent properties of diblock copolymer were increased to approach maximum values. This phenomenon proves the propensity of polymer for fluorine enrichment at air-polymer surface.     

Surface properties of polymethylenediamine-fixed styrene/acrylic acid copolymer latex

Surface charge density, ζ-potential, and dispersion stability of polymethylenediamine (PMD)-fixed styrene/acrylic acid copolymer [P(St/AA)] latex were investigated. PMD-fixed P(St/AA) latices are amphoteric and have isoelectric points at pH 4–7. Though the flocculations were observed at neutral pH, the pHs where the flocculation rates were maximum are slightly higher than were the isoelectric points. This result suggests the influence of the expansion of PMD-fixed polymer layer surrounding the particles on the flocculation. The fixation of PMD to the surface of P(St/AA) latex lowers the dispersion stability for high electrolyte concentration.     

Calorimetric behavior of methacrylic polymers

Specific heats for poly(methyl methacrylate), poly(diethylaminoethyl methacrylate), poly(cyclohexyl methacrylate), poly(allyl methacrylate), and poly(ethyl acrylate) were measured from 120 to 300°C. with a drop calorimeter. It was found that existing solid-state theories and equations were unable to correlate the data. The reason advanced was that such theories were developed for crystalline materials, which differed greatly from the amorphous polymers of the present work. A more successful approach was to use a correlation technique originally developed for organic liquids.     

Molecular dynamics simulation of polymers adsorbed onto an alumina surface

This work presents a relatively simple simulation procedure to demonstrate the effects of polymers on an alumina surface. The procedure employs molecular dynamics (MD) techniques to execute real-time simulations on the interactions of polyolefin, polyacrylate, polyoxide, polyol, and polyphenyl linkages with an idealized alumina surface. According to the technique, the adsorption energy is dependent on the geometrical structure of the monomers and decreases for polymer chains with alkyl side-groups in the backbone, but increases for those with functional groups. The results from this simulation procedure indicate that polymer chains with more -CH₂- or functional groups in the framework can markedly increase the adsorption energy. In addition, polyphenyl linkages reveal a wide range of the low-energy region in the rotations of torsional angles. The result is a favorable deformation of the polymer chains with phenylenes in the backbone, thereby leading to a large adsorption energy.     

NMR study of adsorbed water on acrylic acid-grafted and methacrylic acid-grafted cellulose

The water-adsorbing properties of cellulose samples which had been graft copolymerized with hydrophilic vinyl monomers using ceric salt as an initiator were investigated by means of the width of the high-resolution NMR absorption spectrum, water retention, and moisture regain of the samples. In the change of the width at half-value of the spectrum with per cent grafting, a maximum value followed by a minimum value was observed on samples both grafted with acrylic acid and methacrylic acid. Thus, the effect of grafting on the water-adsorbing properties appeared not to be simple. Though no special change in the water retention by grafting was observed, the per cent grafting dependence on the moisture regain in high relative humidity showed a peculiar and definite relation. The per cent grafting giving maximum moisture regain was about 8% and 18% for acrylic acid and methacrylic acid, respectively, and this agreed very well with the minimum widths at half-value. The change in the glass transition temperature of the sample—water system caused by grafting is also described.     

Change in surface properties of polymers with immersion in sulfuric acid

By using a similar apparatus to that described by Baer and McLaughlin but differing in detail, the surface characteristics of samples of polyethylene, polypropylene, and a woven glass fiber/polyester laminate have been studied after periods of immersion in sulfuric acid at 60°C. Results show considerable progressive variation over the range of immersion times employed (up to 170 hr.), suggesting that surface changes might be considered as a measure of the corrosion involved. (No measure of the corrosion was attempted). The presence of a water layer on the surface of the test piece is suggested as being the reason for the plot of sin α_s versus V^-2/3 giving an intercept on the sin α_s axis whereas in the original work of Baer and McLaughlin the plot passes through the origin.     

聚丙烯蜡接枝甲基丙烯酸和苯乙烯接枝率的测定

考查了聚丙烯蜡接枝甲基丙烯酸、苯乙烯反应中,不同接枝率的红外特征峰的变化规律。通过特征峰比值和化学滴定所测接枝率值的线性回归,建立了相应的半定量经验方程式,建立了用红外法对聚丙烯蜡的接枝率进行半定量分析的方法,     

Soap-free emulsion polymerization of styrene using poly(methacrylic acid) macro-RAFT agent

A well-defined poly(methacrylic acid) (PMAA) macro-RAFT agent has been synthesized by the bulk polymerization using 4-toluic acid dithiobenzoate as a RAFT agent and successfully employed as a reactive emulsifier in the soap-free emulsion polymerization of styrene, leading to a formation of stable latex. The amphiphilic block copolymer, prepared from the in situ micelle formation, contains a hydrophilic PMAA block and a hydrophobic PS block, via styrene monomer transfer reaction to the dithioester function in PMAA macro-RAFT agent during the nucleation step. The chemical structure of the synthesized PS with the PMAA macro-RAFT agent was confirmed using FTIR and NMR. In addition, it was confirmed that the macro-RAFT agent is present on the particle surface via the ESCA measurement. The reaction mechanism was proposed that the stable spherical particles enlarged by the aggregation of small particles, which were also produced by the chemical or physical bonding between the tiny small particles. The results indicate that the PMAA macro-RAFT agent is used as emulsifier for the formation of PS particles and block copolymer [P(S-b-MAA)] in situ.     

Synthesis and surface properties of amphiphilic fluorine-containing diblock copolymers

Amphiphilic diblock copolymers (DCs) of 2,3,4,5,6-pentafluorostyrene (PFS) and 2-hydroxyethyl methacrylate (HEMA) of different composition and molecular weights were prepared by two-step reversible addition–fragmentation chain transfer (RAFT) polymerization and first used for preparation of superhydrophobic coatings for cotton/polyester fabrics. The transition from hydrophobic to superhydrophobic coatings is controlled by the ratio between poly(2,3,4,5,6-pentafluorostyrene) (PPFS) block and poly(2-hydroxyethyl methacrylate) (PHEMA) block lengths (P_n^PFS/P_n^HEMA). The increase in P_n^PFS/P_n^HEMA is accompanied by a significant increase in water (θ^Н₂^О) and diiodomethane (θ^CH₂^I₂) contact angles, which reach the plateau at P_n^PFS/P_n^HEMA = 3.5 and remains almost constant up to P_n^PFS/P_n^HEMA = 6.2. Surface modification of the cotton/polyester fabric with the DC having P_n^PFS/P_n^HEMA = 6.2 produced superhydrophobic surface with θ^Н₂^О = 158 ± 4° and contact angle hysteresis CAH = 5 ± 2°, and θ^CH₂^I₂ = 107 ± 3°.     

Synthesis and polyelectrolyte behavior of poly(methacrylic acid) star polymers

Poly(tert‐butyl methacrylate) [P(tBMA)] star polymers were synthesized by copolymerization of p(tBMA) macroinitiator with ethylene glycol dimethacrylate via atom transfer radical polymerization method. P(tBMA) stars had a narrow molecular weight distribution (M_w/M_n = 1.06–1.15). The ratio of radius of gyration to hydrodynamic radius R_G/R_H, which indicates inner segment density, was in the range 1.16–1.22 in tetrahydrofuran (THF) (arm number f = 25–142). These stars behaved not as hard spheres but as soft spheres in THF. Poly(methacrylic acid) stars were obtained by the hydrolysis of P(tBMA) arms. We investigated the conformation of star polyelectrolyte as a function of pH and ionic strength by means of dynamic light scattering (DLS). The hydrodynamic diameter increased gradually from 18.8 to 48.3 nm as a function of the solution pH. In addition, we compared experimental results with theoretical models for star polyelectrolytes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Microsphere synthesis by emulsion copolymerizations of styrene with poly(methacrylic acid) macromonomers

The polymer microspheres were synthesized by emulsion copolymerizations of styrene with vinyl benzyl terminated poly(methacrylic acid) (PMA) macromonomers in an aqueous ethanol solution. In these copolymerization systems, the macromonomer acted not only as a comonomer but also as a stabilizer. The particle diameters obtained from the water‐soluble initiator system showed smaller values than those obtained from the water‐insoluble initiator system. These polymer microspheres had a very narrow particle‐size distribution. The particle diameters depended strongly on the feed amount and molecular weight of PMA macromonomers, water fraction in the mixed solvent, and pH in the medium. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 900–905, 2002