The surface properties of ionomers based on styrene-co-acrylic acid copolymers

The surface properties of styrene-co-acrylic acid copolymers and of the obtained ionomers containing alkali metal ions, before and after UV-irradiation, were investigated by the measurements of water contact angles and ATR-FTIR spectroscopy.It was examined, how the content and nature of the alkali metal introduced into the initial copolymer influences the water contact angle, surface free energy and its components, polar and dispersive.It was ascertained that the water contact angle, surface free energy and its components depend on the content of introduced acid or salt. These values were practically independent of the nature of the alkali metal introduced into the copolymer. However, more considerable changes were observed for the ionomers containing sodium ions.The research has indicated that UV-irradiation causes the increase in surface hydrophilicity of the investigated ionomers.     

Preparation and Surface Properties of Fluorinated Acrylates Copolymers

Copolymerization of acrylates and styrene (St) with perfluorooctylacyloxyethyl methacrylate (FA) monomer, prepared from the reaction of perfluorooctanoic acid and hydroxymethyl methacrylate, was carried out by solution polymerization. The fluorinated acrylate and St copolymers (PFA) were examined by GPC, FT-IR, and ¹H NMR. The surface tension of the PFA solution in N-methyl pyrrolidone was tested by the drop volume method. The results showed that the surface tension of the PFA solution decreased in exponential decay with increase of the PFA concentration, and the surface tension of the solution also decreased with increased addition of the FA monomer in the copolymer at the same concentration. Meanwhile, the adsorption of the PFA macromolecules in the air–solution interface increased and enrichment of the fluorinated segments on the solution surface occurred. The studies of the surface free energy, polarity, fluorine content, and morphology of the PFA films illustrated that the surface free energy and polarity of the PFA films were decreased with the augment of the FA monomer in the copolymers, and that the fluorine content and the surface roughness were increased. The surface free energy of the PFA film was as small as 16.6 mN·m^?1. The surface properties of the PFA copolymers obtained by one shot feed during polymerization were superior to those obtained by continuing feed procedure. More fluorine segregation occurred and induced the formation of a fluorine-enriched surface if the PFA copolymer was postheated. The posttreatment was thus beneficial to the improvement of the surface properties of the PFA film.     

Free-radical copolymerisation of acrylamides,acrylates, and α-olefins

We report the results of a joint theoretical and experimental investigation into the copolymerisation of acrylamides and acrylates with α-olefins in free-radical processes. The transition-state structures of models for free-radical homo- and copolymerisation involving acrylamide, methylacrylamide, methacrylate, methyl methacrylate, and ethylene have been determined using density functional theory. The reaction energies and barrier heights comport with the experimentally observed properties, including the prevalence of monomer alternation, the realised stereospecificity, and the reaction yield. Continuum solvation models have been applied to determine the sensitivity of the relative energies to the bulk solvent properties. Experimentally, a Lewis acid catalyst is demonstrated to increase the incorporation of nonpolar 1-alkenes in copolymerisations with polar acrylamides and acrylates. In the presence of the Lewis acid, scandium (III) trifluoromethanesulfonate, the copolymerisation of 1-hexene and acrylamide results in an 8.5 mol % incorporation, up from 3.9 mol % in the absence of the Lewis acid. Computations incorporating Mg²⁺ as a model Lewis acid elucidate the mechanism of this catalysis. In the addition of methacrylate to a methyl methacrylate radical terminated polymer, the Lewis acid binds to the carbonyls on both promoting isotactic addition, while for the addition of an alkene to the same polymer, the Lewis acid binds to the polymer, reducing the barrier for alkenyl addition inductively by withdrawing electron density. We have demonstrated the ability of computational studies to aid experimentalists in the synthesis of new copolymers with desired properties.     

Contact charging of coatings of ionomer/polymer blends

Contact charge experiments using successive single contacts with a metal contact were performed on coatings of polystyrene-co-butyl methacrylate blends containing a pyridinium toluenesulfonate ionomer or a partially sulfonated polystyrene copolymer. The charging response to the ion pair content of the coatings was similar to the response reported for powders with the same compositions, which were charged by rolling the powders with metal beads. In general, an increase in the charging capacity of the coatings was observed after a mild thermal treatment. Exposure of the coatings to an oxygen plasma treatment had a large effect on the charging capacity of the coatings containing the partially sulfonated polymer, and only a small effect on the coatings containing the pyridinium toluenesulfonate ionomer.     

Dielectric properties of a hydrated sulfonated poly(styrene-ethylene/butylenes-styrene) triblock copolymer

The present study showed that sulfonated poly(styrene-ethylene/butylenes-styrene) (S-SEBS) triblock copolymer ionomers can be made to exhibit dielectric constants on the order of a hundreds thousand. Although they are too lossy at this point to use as dielectric materials in capacitors or as electrostrictive Maxwell effect transducer materials because of their high hydrogen ion conductivity, the results of these initial dielectric studies as a function of ion content were used to try to understand the effects of a polar plasticizer, water, on dielectric properties of the acid form of this ionomer. This was done before moving on to more tightly bound ions (rather than the hydrogen ions of the sulfonic acid groups used here) and to other polar, less mobile plasticizers (which also interact strongly with the ionic dipoles). The discovery of such high dielectric constants suggested the possibility that low dielectric loss versions of this type of polymer, as well as other members of the class known as ionomers, might find future applications as extremely high dielectric constant materials in capacitors or transducers. Experimental results for films with degrees of sulfonation on the order of 10% or more showed dielectric constants on the order of ?′ ∼ 100,000 but dielectric loss tangents near D = tan δ ∼ 0.3, when the materials were exposed to high humidity conditions. Experiments to determine the effects of water content on the material's dielectric response showed that water can easily move into and out of the films studied and that this transport behavior is strongly correlated to the relative humidity of the environment and to the degree of sulfonation. Water content, in this case, was thus the primary consideration when attempting to understand the observed high dielectric constants in films with degree of sulfonation greater than 5.5%. However, vacuum-dried films were, also, examined and observed to exhibit a dielectric constant on the order of 2 until the degree of sulfonation was greater than 11%. Above this value, the dielectric constant increased by approximately 100% to a value on the order of 4.     

Laser performance of pyrromethene 567 dye in solid matrices of methyl methacrylate with different comonomers

Laser performance of pyrromethene 567 (PM567) dye dissolved in pure poly(methyl methacrylate) homopolymer and its copolymers with 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 1-vinyl-2-pyrrolidone, 2-phenoxyethyl acrylate, and 2,2,2-trifluoromethyl methacrylate has been investigated. The chosen monomers were selected to mimic solvents used in a previous study on the photophysical and lasing properties of PM567 in liquid solution in order to establish correlations between the lasing properties of PM567 in liquid and solid solutions. The vol/vol proportion of the different comonomers in each copolymer formulation was systematically varied, and the effect of each composition on the lasing properties of PM567 was evaluated. The laser samples were transversely pumped at 534 nm with 5.5-mJ pulses from a frequency-doubled Q-switched Nd:KGW laser. Lasing efficiencies of up to 30% and good photostabilities, with a drop of the initial laser output of 20% after 10000 pump pulses in some of the solid samples, were demonstrated. Received: 2 June 1999 / Revised version: 18 July 1999 / Published online: 3 November 1999     

Molecular and supramolecular structure of sulfonated polystyrene ionomers in solutions

The structure of sulfonated polystyrene ionomers in chloroform was studied by molecular hydrodynamics and neutron scattering methods. The ionomer containing 1.35 mol % of ionogenic SO₃Na groups undergoes the coil-globule transition and transforms to a micellar structure due to attraction of polar groups concentrated in the core surrounded by nonpolar chain fragments. At a sulfonation degree of 2.6 mol %, selfassembly of SO₃Na groups with adjacent chain segments to the structure such as a spherical layer, i.e., vesicle (hollow micelle with solvent) with boundaries formed by nonpolar chain fragments, is observed. Vesicular structures in solution associate in pairs. Intra- and interchain associations are significantly enhanced by hydrogen bonds in ionomers with acid groups SO₃H (2.6 and 4.47 mol %) which stabilize micellar structures, promoting their assembly into chain clusters and fragments of the simple cubic lattice.     

Melt flow and mechanical properties of sulfonated sbr ionomers and their polymer blends

Highly unsaturated rubber, styrene-butadiene rubber (SBR), was sulfonated successfully by sulfuric acid and acetic anhydride as sulfonating agent in a mixed solvent of petroleum ether and methyl ethyl ketone at high concentration, and neutralized with metallic acetate to form ionomer. Melt flow and mechanical properties of the ionomers and their blends with other polymers were studied. The results showed that the SBR ionomers can be melt processed easily in the presence of zinc stearate and that they behave like thermoplastic elastomers. Zinc stearate lowered the melt viscosity represented by the torque value of a Brabender mixer, and increased both the flow activation energy and the tensile strength of the ionomer. Sulfonate content of the ionomer enhanced both the melt viscosity and tensile strength. Type of cations used in neutralization significantly affected the properties of the ionomers. Blends of the ionomer with polypropylene or SBS showed synergistic behavior with respect to tensile strength, whereas those with polystyrene or cis-1,4-polybutadiene exhibited antagonistic behavior.     

Preparation and Properties of Chlorinated Polyethylene-Chlorinating/Grafting-Poly (Acrylic acid) and its Sodium-Salt Ionomer

Acrylic acid (AA) was grafted onto high-density polyethylene (HDPE) by in-situ chlorination graft copolymerization (ISCGC), yielding a graft copolymer composed of chlorinated polyethylene (CPE) as backbone and poly (acrylic acid) (PAA) as branch chains. The reaction process and the preparation of its carboxylated ionomers were studied. The structure of the graft copolymer and the ionomer were characterized by FTIR, gel permeation chromatography (GPC), and degree of grafting (GD). The influence of factors related to the main and side reactions, including the monomer concentration, chlorine contents of the product, and reaction temperature were investigated. Additionally, the effects of these factors on the reaction are described. The aim of the research was to investigate how chlorinated polyethylene grafted with poly (acrylic acid) (CPE-cg-PAA) and its sodium-salt ionomer could be prepared and their relative effect on thermal and mechanical properties.     

Nano-network with dual temperature and pH responsiveness based on copolymers of 2-hydroxyethyl methacrylate with 3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]-undecane

Abstract  

This study refers to the synthesis of a nano-network with dual temperature and pH responsiveness based on the 2-hydroxyethyl methacrylate (HEMA) copolymers with a comonomer with spiroacetal moiety and crosslinking capacity, namely 3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]-undecane (U). The copolymers were synthesized by radical emulsion polymerization, using 4,4′-azobis(cyanopentanoic acid) as initiator, in the presence of sodium lauryl sulfate as tensioactive agent and poly(vinyl alcohol) as protective colloid. Three copolymer variants were taken into study resulted from the different ratio between the comonomers (HEMA/U), which was about 98/2, 95/5, and 90/10, respectively. The copolymers were characterized by FTIR and thermal analysis. The copolymers sensitivity was evidenced by studying the evolution of the hydrodynamic radius and zeta potential of the polymeric particles as a function of pH. Thus, the particles size increases with the comonomer amount, from 193 nm in case of the homopolymer up to 253 nm for the copolymer with maximum content of the comonomer (10%). The increase of the particle hydrodynamic radius with the growth of temperature was also put into evidence.