Synthesis and characterization of miktoarm star copolymer of styrene and butadiene using multifunctional macromolecular initiator

A new kind of multifunctional macromolecular initiator with Sn-C bonds and polydiene arms was synthesized by living anionic polymerization. At first, polydiene-stannum chloride （PD-SnCl3） was prepared by the reaction of n-butyl-Li （n-BuLi）, stannic chloride （SnCl4） and diene. Then PD-SnCl3 was used to react with the dilithium initiator to prepare the multifunctional organic macromolecular initiators. The result suggested that the initiators had a remarkable yield by GPC, nearly 90%. By using these multifunctional macromolecular initiators, styrene and butadiene were effectively polymefized via anionic polymerization, which gave birth to novel miktoarm star copolymers. The relative molecular weight and polydispersity index, microstructure contents, copolymerization components, glass transition temperature （Tg） and morphology of the miktoarm star copolymers were investigated by GPC-UV, ~H NMR, DSC and TEM, respectively. 2009 Xing Ying Zhang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

CONTROLLED RADICAL COPOLYMERIZATION OF STYRENE AND MALEIC ANHYDRIDE UNDER GAMMA RADIATION IN THE PRESENCE OF BENZYL DITHIOBENZOATE

The copolymerization of styrene (St) with maleic anhydride (MAh) under gamma radiation at room temperature in the presence of benzyl dithiobenzoate (BDTB) was found to display 'living' nature evidenced by constant concentration of chain radicals during the copolymerization, linear evolution of molecular weights with conversion and narrow molecular weight distribution (M-w/M-n = 1.23-1.35). The compositional analysis and the sequence structural information of the copolymers obtained from DEPT (Distortionless Enhancement by Polarization Transfer) experiments demonstrate that the copolymers obtained also possess strictly alternating structure.

Epoxidation of Styrene-Isoprene-Styrene Block Copolymer and Research on Its Reaction Mechanism

Styrene-isoprene-styrene（SIS） block copolymer was modified into epoxidized styrene-isoprene-styrene（ESIS） block copolymer with performic acid generated in situ from hydrogen peroxide and formic acid.The structure and property of ESIS were characterized by Fourier transform infrared（FT-IR） spectroscopy,gel permeation chromatography（GPC）,thermogravimetric/differential thermogravimetric（TG/DTG）,melt flow rate（MFR） and dynamic mechanical analysis（DMA）,and the reaction mechanism in the process of epoxidation was analyzed.The results showed that C=C double bonds of 1,4-structure were more active than that of 3,4-structure in polyisoprene chains.With epoxidation reaction proceeding,the whole tendency of molecular weight increased and molecular weight distribution widened,and MFR firstly increased and latterly decreased.The heat resistance of ESIS was superior to that of SIS.When SIS was changed into ESIS with 15.3% of mass fraction of epoxide groups,Tg of polyisoprene chains increased from-45.3 ℃ to 10.9 ℃.In the earlier period of epoxidation,some molecular chains ruptured and new substances with low molecular weight formed.However,in the latter period,crosslinking reaction between molecular chains which was initiated by epoxide groups or C=C double bonds occurred and crosslinked insoluble substances came into being.

Synthesis of polystyrene-styrene/butadiene diblock copolymers via reversible addition-fragmentation chain transfer miniemulsion polymerization

Polystyrene-styrene/butadiene diblock copolymers were synthesized via reversible addition-fragmentation chain transfer （RAFT） miniemulsion polymerization.During the polymerization process,the molecular weight distribution was narrow and the numerical molecular weight of the copolymers increased with increasing conversion of monomers,which was close to the theoretical.FT-IR and ^1H NMR results indicated that the microstructure of the polymer was mainly 1,4-trans-butadiene with small amount of 1,2-units,and composition in the copolymers was obtained.

MECHANISM-TRANSFORMATION SYNTHESIS AND CHARACTERIZATION OF POLY(STYRENE-b-2-ETHYL-2-OXAZOLINE) DIBLOCK COPOLYMER

By mechanism-transformation (anionic --> cationic) poly(styrene-6-2-ethyl-2-oxazoline) diblock copolymer, PS-b-PEOx, was synthesized in two steps. The first step is the polymerization of styrene block capped with ethylene oxide and its tosylation; the second step is the cationic ring-opening polymerization of 2-ethyl-2-oxazoline. The products were thoroughly characterized by various methods, such as H-1-NMR, IR, DMA, TEM and SAXS. The results show that the copolymer obtained possesses high molecular weight and narrow molecular weight distribution.

Copolymerization of N-4-Dibenzoylmethane Maleimide with Styrene

The copolymer of N-4-dibenzoylmethane maleimide (p-DBMI) with styrene (St) was prepared and characterized by gel permeation chromatography, thermal analysis and spectroscopy.

DETERMINATION OFTHE CRYSTALLINITY IN DIFFERENT TYPE POLY (OXYETHYLENE-STYRENE)BLOCK COPOLYMERS BY X-RAY DIFFRACTION METHOD

By means of the intensity theory of X-ray scattering and the two-phase concept of high polymer, the basic formula of the crystaUinity in block copolymers has been proposed after the corrections of atomic, temperature, absorption, Lorentz and polarization factor. Application of this method to different type poly (oxyethylene-styrene)block copolymers and the same type block copolymers with different EO contents indicates that the crystallinity in poly (oxyethylene-styrene ) block copolymers increases with the increase of the EO content and decreases in the order: PEO-PS-PEO>PEO-PS>PS-PEO-PS.

STUDY ON STYRENE-BUTADIENE BLOCK COPOLYMER FOR THE MODIFICATI0N OF TIRE TREAD

This paper mainly deals with the design and synthesis of a novel styrene-butadieneblock copolymer. When this copolymer is used in the tread portion of tyres, it can improvewet skid resistance and reduce rolling resistance without sacrificing its general physical-mechanical properties. The visco-elastic curve of tire tread using the novel copolymer asits rubber portion was showed. Reactivity ratios for two monomers in the polymerizingsystem were calculated. The diagrams of differelitial, integral and finite difference calculithroughout the whole molecular chain were presented. The influence of the micro- andmacro-structure of the copolymer chain on wet skid resistance and rolling resistance wasdiscussed

Study on N-Phenylmaleimide/Styrene /Acrylonitrile Copolymer Prepared by Emulsion Polymerization

The emulsion polymerization of N-phenylmaleimide, Styrene and acrylonitrile was studied. The thermal property of this copolymer was measures by dynamic thermomechanical analysis(DMA). The mechanical properties, such as tensile strength, hardness and fie-cural Strength were StUdied experimentally. The results indicated that not only the monomer component but also the polymerization technologies have effect on the properties of the copolymer. The optimum monomer content and suitable polymerization method were obtained.

GRAFTED STYRENE-DIVINYLBENZENE COPOLYMERS CONTAINING BENZALDEHYDES AND THEIR WITTIG REACTIONS WITH VARIOUS PHOSPHONIUM SALTS

A chloromethylated styrene-divinylbenzene copolymer support system functionalized with 4-benzaldehyde and 2-benzaldehyde was prepared. The degree of functionalization with aldehyde groups is well suited for the subsequent use of the products as Wittig reagents. The polymer bound aldehyde was reacted with Wittig reagents to give olefin groups grafted on styrene-divinylbenzene copolymers. The reactions were carded out in phase transfer catalysis conditions. A simple procedure for the calculation of the degree of functionalization and the statistical modeling of the structural repetitive unit of the copolymer are reported.

SYNTHESIS AND CHARACTERIZATION OF POLY(STYRENE - ETHYLENE OXIDE) DIBLOCK COPOLYMERS

Well - defined diblock copolymers Of styrene (St ) and ethylene oxide (EO )have been prepared by sequential living anionic polymerization of the twocomonomers in THF. Diphenyl methyl potassium has been used as initiator. Theblock copolymers were characterized in detail by methods Of size exclusion chromatography (SEC ) , 1H - Nab, FT - IR, dynamic mechanical analysis(Daal ) and WAXD.

Synthesis and performance of miktoarm star copolymers of styrene and butadiene

A novel multifunctional macromolecular organolithium initiator （PD-Sn-（RLi）3） was prepared via living anionic polymerization and used for the synthesis of miktoarm star copolymers in cyclohexane. The average molecular weight, polydispersity index, microstructure and unit composition of the miktoarm star copolymers were characterized with GPC and 1H-NMR. Performances of the miktoarm star styrene-butadiene rubbers were investigated in comparison with those of the blend rubbers such as the tin-coupled star-shaped random copolymers of styrene-butadiene rubber（S-SBR）/natural rubber （NR） blend rubber and S-SBR/Cis-1, 4-polybutadiene rubber （Cis-BR） blend rubber.

Thermal Stability Improvement and Structural Change of Oil Gels Formed by Styrene-Butadiene-Styrene Triblock Copolymer Induced by Adding Poly(phenylene ether)

The thermal stability of oil gels formed by styrene-butadiene-styrene triblock copolymer (SBS) was improved by adding a small amount of poly(phenylene ether) (PPE), which has a higher glass transition temperature (Tg). In naphthenic oil which is a good solvent for the butadiene blocks, but a non-solvent for the styrene blocks and PPE, PPE was selectively included into styrene blocks in SBS, and induced the increase of the Tg of these blocks. The melting temperature determined by viscoelastic measurements and softening temperature of the gels were elevated by adding PPE, while no significant change was detected by adding polystyrene. The gel became opaque by adding PPE, and partially separated phases were observed by field emission scanning electron microscopy (FE-SEM). The dependence of the viscoelastic behavior on the PPE concentration can be explained by the structural change observed by FE-SEM.

New Catalyst for the Copolymerization of Styrene with Carbon Monoxide

Neodymium phosphonate [Nd(P-204)(3)] combined by di(n-butyl) magnesium [Mg(n-Bu)(2)] with hexamethylphosphoramide (HMPA) was first found to be an effective catalyst. The results of infrared spectrum and elemental analysis showed that the copolymers containing carbonyl group were produced.

Volatile Substances in Polymer Toys Made from Butadiene and Styrene

The residual levels and migration behavior of volatile substances were detected using HS-GC/MS for acrylonitrile-butadiene-styrene copolymer (ABS) toys, thermoplastic elastomer toys, and rubber toys made from 1,3-butadiene and styrene found on the Japanese market. The maximum residual level of these volatile substances was 2600 μg/g of styrene in ABS toys. In particular, the levels of known carcinogens 1,3-butadiene, benzene, and acrylonitrile are 5.3, 2.5 and 55 μg/g, which are much lower than the EU limit of 0.1%. Furthermore, some volatile substances migrated from ABS toys into water in amounts of 3 -40 ng/mL. Thermoplastic elastomer toys and rubber toys contained these volatile substances at significantly lower levels than ABS toys.

SYNTHESIS OF POLY(METHYL METHACRYLATE)-graft-POLYSTYRENE BY ATOM TRANSFER RADICAL POLYMERIZATION

The radical copolymerization of methyl methacrylate and 2-hydroxyethyl methacrylate was carried out via atomtransfer radical polymerization (ATRP) initiated by ethyl 2-bromoisobutyrate and catalyzed by CuBr/2,2'-bipyridinecomplex. This polymerization proceeds in a living fashion with controlled molecular weight and low polydispersity. Theobtained copolymer was esterified with 2-bromoisobutylryl bromide yielding a macroinitiator, poly(methyl methacrylate-co-2-hydroxyethyl methacrylate-co-2-(2-bromoisobutyryloxy)ethyl methacrylate), and its structure was characterized by ~1H-NMR. This macroinitiator was used for ATRP of styrene to synthesize poly(methyl methacrylate)-graft-polystyrene. Themolecular weight of graft copolymer increased with the monomer conversion, and the polydispersity remained relatively low.The individual grafted polystyrene chains were cleaved from the macroinitiator backbone by hydrolysis and the hydrolyzed product was characterized by ~1H-NMR and GPC.

Comparison of Two Methods in Determining the Composition Distribution of SBS Copolymers

The comparison of the determination of chemical composition distributions of butadiene-styrene copolymers, obtained by the formula method and experimental method of GPC, is given in this paper. The relative error of average composition was shown to be less than 5%. The formula method was found to be a more convenient and time-saving approach in the characterization of the copolymer composition distribution.

Studies on Rheological, Thermal, and Mechanical Properties of Polylactide/Methyl Methacrylate-Butadiene-Styrene Copolymer/Poly(propylene carbonate) Polyurethane Ternary Blends

Polylactide(PLA),methyl methacrylate-butadiene-styrene copolymer(MBS),and poly(propylene carbonate)polyurethane(PPCU)were blended and subjected to blown film process.The rheological,mechanical,morphological,thermal,and crystalline properties of the PLA/MBS/PPCU ternary blends and the mechanical properties of the resulting films were studied.Results of mechanical test showed that PPCU and MBS could synergistically toughen PLA.The impact strength of 50/10/40 PLA/MBS/PPCU blend(74.7 k J/m^2)was about 7.5 times higher than that of the neat PLA(10.8 k J/m^2),and the elongation at break of 50/10/40 PLA/MBS/PPCU blend(276.5%)was higher by about 45 times that of PLA(6.2%).The tear strength of PLA/MBS/PPCU films was 20 k N/m higher than that of PLA,and the elongation at break(MD/TD)of 50/10/40 PLA/MBS/PPCU films was 271.1%/222.3%,whereas that of PLA was only 2.7%/3.0%.POM observations displayed that the density of spherulite nucleation increased and the size of crystalline particles decreased with the addition of MBS.With increasing PPCU content from 5%to 20%,the density of spherulite nucleation increased and the size of crystalline particles decreased continuously,but the nucleation density of spherulites was slightly lowered with increasing PPCU content from 30%to 40%.The PLA/MBS/PPCU films exhibited excellent mechanical properties,which expanded the application range of these biodegradable films.

Polypyrrole-coated styrene-butyl acrylate copolymer composite particles with tunable conductivity

A series of near or monodisperse styrene-butyl acrylate (SBA) copolymer latex particles with different butyl acrylate contents were coated with polypyrrole. The struc- ture of the SBA/PPy composites was characterized by trans- mission electron microscopy (TEM), scanning electron mi- croscopy (SEM), diffuse reflectance infrared Fourier trans- form spectroscopy (DRIFT), X-ray photoelectron spectros- copy (XPS), differential scanning calorimetry (DSC) and standard four-probe method. The core-shell morphology of the SBA/PPy composite particles was confirmed. The result of DSC showed that Tg of the composite is mainly determined by the core component. The effects of the concentration of polypyrrole, the butyl acrylate content in SBA copolymer and the nature of the counter-anion on the electrical conduc- tivity of compression-moulded samples were studied. It was first found that the electrical conductivity of the samples can be tuned by varying the butyl acrylate content in SBA co- polymer and the highest conductivity of the core-shell com- posite was 0.17 S·cm?1.