Styrene Content Of Copolymer Research Articles

Extruded thermoplastic elastomers styrene–butadiene–styrene/carbon nanotubes composites for strain sensor applications

Tri-block copolymer styrene–butadiene–styrene (SBS) composites with different butadiene/styrene ratios and multi-walled carbon nanotubes (MWCNTs) can be used for the development of electro-mechanical sensors for large strains applications. Extruded CNT/SBS composites show percolation thresholds around 5wt%, electro-mechanical properties with high sensibility at larger strain and the gauge factor reach values up to 30 at strains of 20%. The butadiene/styrene ratio has influence in the mechanical and electro-mechanical properties. In one hand, the increase of the styrene content in copolymer increasing initial mechanical modulus, on the other hand, the increase of the butadiene content leads to larger maximum deformations and higher electro-mechanical sensibility for strains up to 20%. Further, applied initial pre-stress increases the electro-mechanical sensibility of the composites.

Surface Self-Assembled PEGylation of Fluoro-Based PVDF Membranes via Hydrophobic-Driven Copolymer Anchoring for Ultra-Stable Biofouling Resistance

Stable biofouling resistance is significant for general filtration requirements, especially for the improvement of membrane lifetime. A systematic group of hyper-brush PEGylated diblock copolymers containing poly(ethylene glycol) methacrylate (PEGMA) and polystyrene (PS) was synthesized using an atom transfer radical polymerization (ATRP) method and varying PEGMA lengths. This study demonstrates the antibiofouling membrane surfaces by self-assembled anchoring PEGylated diblock copolymers of PS-b-PEGMA on the microporous poly(vinylidene fluoride) (PVDF) membrane. Two types of copolymers are used to modify the PVDF surface, one with different PS/PEGMA molar ratios in a range from 0.3 to 2.7 but the same PS molecular weights (MWs, ∼5.7 kDa), the other with different copolymer MWs (∼11.4, 19.9, and 34.1 kDa) but the similar PS/PEGMA ratio (∼1.7 ± 0.2). It was found that the adsorption capacities of diblock copolymers on PVDF membranes decreased as molar mass ratios of PS/PEGMA ratio reduced or molecular weights of PS-b-PEGMA increased because of steric hindrance. The increase in styrene content in copolymer enhanced the stability of polymer anchoring on the membrane, and the increase in PEGMA content enhanced the protein resistance of membranes. The optimum PS/PEGMA ratio was found to be in the range between 1.5 and 2.0 with copolymer MWs above 20.0 kDa for the ultrastable resistance of protein adsorption on the PEGylated PVDF membranes. The PVDF membrane coated with such a diblock copolymer owned excellent biofouling resistance to proteins of BSA and lysozyme as well as bacterium of Escherichia coli and Staphylococcus epidermidis and high stable microfiltration operated with domestic wastewater solution in a membrane bioreactor.

Biofouling Resistance of Ultrafiltration Membranes Controlled by Surface Self-Assembled Coating with PEGylated Copolymers

Block and random PEGylated copolymers of poly(ethylene glycol) methacrylate (PEGMA) and polystyrene (PS) were synthesized with a controlled polydispersity using an atom transfer radical polymerization method and varying molar mass ratios of PS/PEGMA. Two types of PEGylated copolymers were self-assembly coated onto the surface of poly(vinylidene fluoride) (PVDF) ultrafiltration membranes for enhancing biofouling resistance. It was found that the adsorption capacities of random copolymers on PVDF membranes were all higher than those of block copolymers. However, the specific and overall protein resistance of bovine serum albumin (BSA) on PVDF membranes coated with block copolymers was much higher than that with random copolymers. The increase in styrene content in copolymer increased the amount of polymer coating on the membrane, and the increase in PEGMA content enhanced the protein resistance of membranes. The optimum PS/PEGMA ratio was found to be close to 2 for the best resistance of protein adsorption and bacterial adhesion on the PEGylated diblock copolymer-coated membranes. The PVDF membrane coated with such a copolymer owned excellent biofouling resistance to BSA, humic acid, negatively surface charged bacteria E. coli, and positively surface charged bacteria S. maltophilia.

Preparation and application of sulfonated poly(1‐octene‐co‐styrene)

AbstractIn this article, 1‐octene and styrene was copolymerized by the supported catalyst (TiCl4/ID/MgCl2). Subsequently, by sulfonation reaction, sulfonated poly(1‐octene‐co‐styrene)s which were amphiphilic copolymers were prepared. The copolymerization behavior between 1‐octene and styrene is moderate ideal behavior. Copolymers prepared by this catalyst contain appreciable amounts of both 1‐octene and styrene. Increase in the feed ratio of styrene/1‐octene leads to increase in styrene content in copolymer and decrease in molecular weight. As the polymerization temperature increases, the styrene content in the copolymers increases, however, the molecular weight decreases. Hydrogen is an efficient regulator to lower the molecular weights of poly(1‐octene‐co‐styrene)s. The sulfonation degree of the sulfonated poly(1‐octene‐co‐styrene)s increased as the styrene content in copolymer increased or the molecular weight decreased. Thirty‐six hour is long enough for sulfonation reaction. The sulfonated poly(1‐octene‐co‐styrene)s can be used as effective and durable modifying agent to improve the wettability of polyethylene film and have potential application in emulsified fuels and for the stabilization of dispersions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Syntheses of dinuclear titanium constrained geometry complexes with polymethylene bridges and their copolymerization properties

The polymethylene bridged dinuclear half-sandwich constrained geometry catalyst (CGC) [Ti(η 5:η 1-C 9H 5SiMe 2NCMe 3)] 2 [(CH 2) n ] ( n=6 ( 10), n=9 ( 11), n=12 ( 12)) have been prepared by treating two equivalents of TiCl 3(THF) 3 with the corresponding tetralithium salts of the ligands followed by oxidation by AgCl. Proton and Carbon-13 NMR spectra of the synthesized complexes provide firm evidence for the anticipated dinuclear structure. The important feature associated with the chemical shift of Carbon-13 NMR is the downfield chemical shift of 63.0 ppm due to the ipso-carbon of t-butyl group bonded at the coordinated nitrogen. In addition the chemical shift of the bridge head carbon at the indenyl ring is shifted toward highfield from 119 to 97 ppm. In order to investigate the catalytic behaviors of the prepared dinuclear catalysts copolymerization of ethylene and styrene was conducted in the presence of modified methylaluminoxane. The prime observance is that their activities increase in the order of 10< 11< 12 which indicates the presence of longer bridge between two active sites contributes to facilitate the polymerization activity of the dinuclear CGC. The melting points of the generated copolymers decrease as the styrene portion in feed increases. An interesting point is that styrene content in copolymers formed by the dinuclear catalysts is actually bigger than that in copolymer formed by the mononuclear CGC, which demonstrates the superior comonomer response of the dinuclear CGC comparing to the normal CGC.

Copolymerization of Butadiene and Styrene with n-Butyllithium and Methyl Substituted Pyridine Mixture

The effects of some methyl substituted pyridine compounds (including prydine, quinoline and β-collidine) on n-butyllithium (BuLi)-initiated copolymerization of butadiene and styrene were examined at 40°C or 50°C in n-hexane (solvent). The weight ratio of butadiene to styrene was 75: 25 and that of the monomer to solvent was 1: 4 in all cases.Addition of a small amount of pyridine (or quinoline) retarded the rate of polymerization but did not change the styrene inclusion profile. When more than equimolar pyridine (or quinoline) was added to BuLi, polymerization did not occur. Addition of 2, 6-lutidine or 3, 4- lutidine was effective in increasing both the rate and the styrene content. Addition of 3, 4- lutidine with same 1, 2-addition content gave far more styrene content than that of 2, 6-lutidine when conversion was less than 60%. A detailed comparison of rates of polymerization with copolymer structures obtained was carried out when 2, 4, 6-collidine, β-collidine and triethylamine (TEA) were used as additives to BuLi. The rate of polymerization and the 1, 2-addition content of copolymer decreased in the following order: 2, 4, 6-collidine>8-collidine>TEA, while the order of effectiveness for inclusion of styrene in the copolymer chain was 8-collidine > 2, 4, 6-collidine > TEA.From the oxidative degradation it was found that addition of 2, 4, 6-collidine, β-collidine or 3, 4-lutidine was effective to produce a random butadiene styrene copolymer. Grass transition temperatures (Tg) of these copolymers were also examined.Butadiene-styrene copolymerizations were carried out bs7 using fifteen methyl substituted pyridines as additives to BuLi under the same conditions. It was found the polymerization rate showed as a whole negative correlation with pKb of each compound and the plots of the 1, 2-addition content vs. the styrene content of copolymer (10∼50% conversion) split into three lines because of a steric effect of the additives (cf. Fig.6).

The mechanism of polymerization in the presence of the organic compounds of alkali metals

THE relationship of the structure of a polymeric chain and, oorrespondln~|y, of the properties of polymers, with ~he nature of the selectea catalyst and medium is an interesting characteristic of the polymerization of monomers under the action of organic components of lithium, sodium and-potaesium. Korotkov and others [1] have shown in the polymerization of butadiene that the fraction of 1,2-structures increases on t he replacement of li thium alkyl by sodium aikyl catadysta, and also on the transition from hydrocarbon to ethyl and dioxane. Tobohky and others [2] likewise established that in the polymerization of isoprene with alkyis and aryls of alkali metals, the poly-isoprene chain structure varies with the transformation of the nature of the metal and the solvent, and is not depend e n t on .the structure of the radical linked with the alb~li metal. They also found that ~he styrene content in copolymers obtained on polymerization with lithium organic compounds of the styrene-butauiiene [1] and styrene-isoprene ~ o m s [3] increases when the hydrocarbon solvent is replaced by ethyl. These authors show that the selective effect is determined by the polarity of the metal-carborL bond of the organo-metallic catalyst. I t is known that in the series LiR, Nal~, KR, the Li-R bond is the least polar. I t may be supposed that in the presence of LiR the interaction of the monomer with the catalyst ~11 be determined both by the electron-donor properties of group R and by the accepter properties of lithium. In the case of a typical anion. mechanism (e.g. NaR ill an ether medium), the growth of the chain is determined by the interaction of a monomer with a carbonian, and, correspondingly, the reactivity of a monomer is determined only by its electron-accepter properties. In such an examination it is to be expected that in a copolymer the content of monomers possessing the greater density of electrons in the binary bond will increase in the transition from sodium-to lithium-organic catalyst, and likewise on replacement of ethyl, amine and similar media by hydrocarbon solvents. To verify this supposition, it was essential to obtain certain quantitative data characterizing the simple sequences of these processes, and also to extend the invest,igation of the influence of polymerization on the composition of a copolymer