Surface properties of block and graft polystyrene–polydimethylsiloxane copolymers

The surface compositions of a series of polystyrene‐b‐polydimethylsiloxane (PS‐b‐PDMS) and polystyrene‐g‐polydimethylsiloxane (PS‐g‐PDMS) copolymers were investigated using ATR‐FTIR and XPS technique. The results showed that enrichment of PDMS soft segments occurred on the surface of the block copolymers as well as on that of graft copolymers. And the magnitude order of the enrichment was as follows: PS‐b‐PDMS > PS‐g‐PDMS, which was attributed to the facilitating of the movement of the PDMS segments in PS‐b‐PDMS copolymer. Meanwhile, the solvent type and the contact medium had influence on the accumulation of PDMS on the surfaces. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Morphology of pyrolysed polystyrene–isoprene–styrene and polystyrene–butadiene–styrene block copolymers

The surface morphology of thermooxidative degraded polystyrene–isoprene–styrene (SIS) and polystyrene–butadiene–styrene (SBS) thermoplastic block copolymers was studied by scanning electron microscopy. Surface changes caused by heating the samples in a pyrolyzer for 15 and 30 min were presented in different micrographs. The morphological changes occurring due to the formation of polar groups and their crosslinking during the thermooxidative degradation are discussed. Morphological study of these thermally degraded polymer samples shows very good correlation with the thermodegradation results. The rate of thermodegradation is fast in case of SBS when compared with SIS block copolymer. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 2549–2553, 2006     

Morphology of pyrolyzed polystyrene–isoprene–styrene and polystyrene–butadiene–styrene block copolymers

The surface morphology of thermooxidative‐degraded polystyrene–isoprene–styrene (SIS) and polystyrene–butadiene–styrene (SBS) thermoplastic block copolymers were studied by scanning electron microscopy. Surface changes caused by heating the samples in a pyrolizer for 15 and 30 min were presented in different micrographs. The morphological changes occurring due to the formation of polar groups and their crossing linking during the thermooxidative degradation are discussed. Morphological study of these thermally degraded polymer samples show very good correlation with the thermodegradation results. The rate of thermodegradation is fast in case of SBS compared with SIS block copolymer. ©2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Thermoelastic properties of block copolymers of the polystyrene–polybutadiene–polystyrene type

The thermoelastic properties of block copolymers of the type polystyrene—polybutadiene—polystyrene were studied. It was found that the fu values depend on the content of styrene and the strain history as well. These relationships are discussed from the point of view of polymer structure.     

Synthesis of amphiphilic polystyrene–ionene diblock copolymers with controlled block lengths

Amphiphilic polystyrene-ionene diblock copolymers with blocks of controlled molecular weights were synthesized by a new method. The preparation starts with the anionic polymerization of styrene with 3-(dimethylamino)propyl-lithium as initiator, yielding tertiary amino end-functionalized polystyrenes of molecular weights that can be varied over a wide range from 1 to 100kg/mol, and a relatively low polydispersity (M?_w/M?_n = 1.1–1.4). The crucial step in this method is the stepwise coupling of the reactive end-group of the polystyrene with bromo- and tertiary-amino-terminated monodisperse oligomeric 2,4-ionenes. The amphiphilic polymers with well-defined block lengths were characterized by thin-layer chromatography, end-group titration and elemental analysis. Amphiphilic block copolymers with a monodisperse ionene block consisting of up to 10 quaternary ammonium groups could be derived.     

Compatibilization efficiency of styrene–butadiene triblock copolymers in polystyrene–polypropylene blends with varying compositions

The compatibilization efficiency of two styrene‐butadiene‐styrene triblock copolymers with short (SB1) and long (SB2) styrene blocks was studied in polystyrene (PS)–polypropylene (PP) blends of composition 20, 50, and 80 wt % PS. The supramolecular structure of the blends was determined by small‐angle X‐ray scattering, and the morphology was studied with transmission electron microscopy and scanning electron microscopy. Structural changes in both the uncompatibilized and compatibilized blends were correlated with the values of tensile impact strength of these blends. Even though the compatibilization mechanisms were different in blends with SB1 and SB2, the addition of the block copolymers to the PS–PP 4/1 and PS–PP 1/4 blends led to similar structures and improved the mechanical properties in the same way. These block copolymers had a very slight effect on the impact strength in PS–PP 1/1 blends, exhibiting a nearly cocontinuous phase morphology. The strong migration of SB2 copolymers to the interface and of SB1 copolymers away from the interface were detected during the annealing of compatibilized PS–PP 4/1 blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2431–2441, 2004     

Characterization of cotton–polystyrene graft copolymers

Characterization of cotton–polystyrene graft copolymers prepared by ceric ion initiation is reported. Various techniques studied include moisture sorption, solubility in cupriethylenediamine (CED), infrared spectra, differential thermal analysis (DTA), electron micrographs and X-ray diffractograms, which point to the existence of true grafting. The graft copolymers showed a slight fall in breaking load and improved resistance to wetting.     

1,2‐propanediol–cellulose–acrylamide graft copolymers

1,2‐Propanediol–cellulose–acrylamide graft copolymers (PCACs) were developed for enhanced oil recovery. They were prepared with acrylamide and 1,2‐propanediol (PDO)–cellulose, which was formed through the addition of glycols to cellulose by the Shotten–Baumann reaction between 3‐chloro‐1,2‐propanediol and cellulose. The graft copolymerization was initiated with a redox system between Ce⁴⁺ and glycols in cellulose. The infrared spectrum of PDO–cellulose had some characteristic absorption bands around 2960 (νC? H) and 1050 cm^?1 (νC? O) that also appeared for the PDO group and pyranose ring of cellulose, respectively. The rate of Ce⁴⁺ consumption by PDO–cellulose was investigated through the calculation of the overall kinetic constant from the slopes of ln(D ? D_R) versus time (where D is the absorbance and D_R is the absorbance of the original polysaccharide solution) The results showed that PDO–cellulose had high reactivity and that there were two mechanisms of oxidation by Ce⁴⁺ with PDO–cellulose. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3022–3029, 2004     

Membranes prepared from keratin–polyacrylonitrile graft copolymers

Graft copolymerization of acrylonitrile onto a soluble wool keratin derivative was studied with the reduced and carboxymethylated low-sulfur protein fraction from wool. Copolymerization was carried out under a variety of conditions with a redox system of (NH₄)₂S₂O₈–Na₂SO₃ in 60% (w/w) aqueous ZnCl₂ solution at 10°C. Monomer conversions higher than 90% were obtained by the stepwise addition of initiator. The graft products were successfully separated into grafted copolymer and homopolyacrylonitrile (PAN) by fractional precipitation or solvent extraction with DMF. Grafted PAN were isolated by acid hydrolysis of the keratin backbone. Characterization of grafted and homo-PAN was carried out by IR spectroscopy, amino acid endgroup analysis, and viscometry. On the basis of the results, effects of polymerization conditions on grafting parameters were discussed. Membranes were prepared from 60% aqueous ZnCl₂ solution by using ice-cold water as the regenerating medium. All the membranes formed from the graft products were transparent. Observation by scanning electron microscopy showed that the surface consisted of rather spherical keratin domains regularly distributed in the PAN matrix. Selective hydrolysis of the keratin domains allowed a new type of porous PAN membrane to be obtained, with the inner walls of the pores being charged with amino acid residues attached to PAN chains as the endgroup.     

Removal of nonionic surfactant by systems based on polystyrene–polyoxyethylene block copolymers

Three polystyrene (PS)–polyoxyethylene (POE) block copolymers were synthesized: S-114 and S-123 as copolymers of POE–PS–POE type, and S-61-10 as that of type. Although the copolymers themselves did not remove nonionic surfactant, polyethylene glycol mono-p-nonylphenyl ether (NP, n = 10), in water, the copolymers, which were supported on activated alumina, removed the surfactant. The removal rates of NP by the copolymers supported on the alumina were compared. The effect of initial concentration of NP and the effect of the amount of supported copolymer on the amount of NP removed were studied. The Freuindlich adsorption isotherm was observed between the residual concentration of NP and the amount of NP removed. In the three copolymers supported on the alumina, the amount of removal per unit mass was the greatest for the S-61-10.     

Shape memory effect of polyethylene/nylon 6 graft copolymers

A series of maleated polyethylene/nylon 6 blends with nylon as the dispersed phase was prepared at 230°C in a batched Haake mixer, and their shape memory effect was investigated. The nylon contents of the blends are in the range from 5 to 20 wt%. The Molau testing was used to verify the in situ formation of polyethylene-g-nylon 6 graft copolymers bridged by maleic anhydride in the melt-blending process. Differential scanning calorimetry, dynamic mechanical thermal analysis and scanning electron microscopy have been used to investigate the crystallization and melting behaviour, dynamic mechanical properties and phase morphology for all the specimens. The results indicate that the maleated polyethylene/nylon 6 blend specimens are able to show good shape memory effect under normal experimental conditions. The high crystallinity of the polyethylene segments at room temperature and the formation of a network structure in these specimens are the two necessary conditions for their good shape memory effect. The nylon domains, which serve as physical crosslinks, play a predominent role in the formation of a stable network structure for the graft copolymers. The studies show that shape memory materials with thermoplastic characteristics can be prepared not only by segmented copolymers but also by graft copolymers, and the reaction processing method might be a promising and powerful technique for this purpose.     

Compatibility of nylon 6 and PMMA–oligoamide graft copolymer

PMMA–oligoamide graft copolymers, which were prepared by reacting poly(methyl methacrylate-co-methacryloyl chloride) with oligoamide, were blended with nylon 6. The compatibility was examined by measuring thermal properties such as melting point and crystallization temperature. It was observed that the melting point was significantly depressed as the grafted PMMA was added to nylon 6, suggesting that the blend is a miscible system. It was concluded that hydrogen bonding between amide groups of the two polymers enhanced the miscibility.     

Formation of phase structure and crystallization behavior in blends containing polystyrene–polyethylene block copolymers

The microphase separation structure in the molten state and the structure formation in crystallization from such ordered melt were investigated for the blends of polystyrene–polyethylene block copolymers (SE) with polystyrene homopolymer (PS) and polyethylene homopolymer (PE) and for the blends consisting of two kinds of SE with different copolymer compositions from each other, using synchrotron small-angle X-ray scattering techniques (SAXS). The copolymer compositions of SE block copolymers employed were 0.34, 0.58 and 0.73 wt. fraction of PE, and their melt morphologies were cylindrical, lamellar and lamellar, respectively. Macrophase separation or the morphology change in the melt occurred depending on the molecular weight and the blend composition, as reported so far. In crystallization from such macrophase-separated and microphase-separated melts, the melt morphology was completely kept for all the blends. Crystallization behavior was also investigated for the blends. The crystallization within the spherical and cylindrical domains surrounded by glassy PS was not observed for SE/PS blends. In the crystallization from the macrophase-separated melt, two exothermal peaks were observed in the DSC measurements, while a single peak was observed for other blends. For the blends with PS, the degree of crystallinity was depressed and the apparent activation energy of crystallization was high, compared to those for the corresponding neat SE. For SE/PE and SE/SE blends, those were changed depending on the blend composition.     

Structural characterisation of some polystyrene—polyisoprene copolymers

The various levels of organisation which may be distinguished in non-crystalline block copolymers are considered. An account is given of the application of low-angle X-ray diffraction and electron microscopy to the characterisation of the two-phase morphology and grain texture of some styrene/isoprene copolymers. The first group of copolymers to be considered contains two series of samples of the type S–I, (S–I–)₂X, (S–I–)₃Y, and (S–I–)₄Z where I is polyisoprene, S polystyrene and X, Y and Z are di-, tri- and tetra-functional coupling groups. The second group of copolymers which was subjected to a less detailed study than the first consists of just two polystyrene-g-polyisoprene samples.     

Mechanical properties of conducting H‐type polysiloxane–polypyrrole graft copolymers and polytetrahydrofuran–polypyrrole block copolymers

The mechanical properties of block copolymers of polypyrrole and pyrrolyl‐ended azobis‐polytetrahydrofuran (TPPy) and graft copolymers of pyrrolyl‐ended H‐type polydimethylsiloxane (SPPy) were investigated and compared with those of polypyrrole (PPy). Conducting films were prepared electrochemically at a constant potential and doped with p‐toluene sulfonate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1663–1666, 2002     

Synthesis of graft copolymers. II. Synthesis of polystyrene‐g‐poly(methyl methacrylate)

The thermolysis of labile 1,2‐bis(trimethylsilyloxy)tetraphenylethane groups pendant along polystyrene chains in the presence of various vinyl monomers leads to the direct synthesis of graft copolymers. Depending on the monomer chosen, the polymerization temperature, and the number of active sites by the macroinitiator molecule, crosslinked or total soluble graft copolymers can be prepared. Several conditions were studied in order to attain soluble polystyrene‐g‐poly(methyl methacrylate) copolymers under a controlled polymerization mechanism. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 12–18, 2002     

Plasma‐enhanced synthesis of maltodextrin–polydimethylsiloxane graft copolymers

Ether‐extracted maltodextrin (MD) powder was surface functionalized under 13.56‐MHz RF–SiCl₄‐plasma conditions, and consecutively in situ aminated and grafted using dichlorodimethylsilane. Survey and high‐resolution X‐ray photoelectron spectroscopy, FTIR evaluations, fluorescence‐labeling technique, SEM, and DTA/TG analyses prove the presence of a graft‐copolymer layer on the modified starch‐granule surfaces and the existence of a significantly changed surface morphology of the starch granules, as a result of the grafting reactions. The hydrophobic nature of the polydimethylsiloxane‐grafted starch and its significantly changed thermal behaviors were also evaluated. Potential applications of modified maltodextrins are discussed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1120–1129, 2001     

Associative properties of perfluorooctyl end‐functionalized polystyrene–poly(ethylene oxide) diblock copolymers

The synthesis of 2,2,3,3‐tetrahydro‐perfluoroundecanoyl end‐functionalized polystyrene–poly(ethylene oxide) block (PS‐block‐PEO‐R_F) copolymers and their matching PS‐block‐PEO diblock copolymers was carried out by sequential anionic polymerization. Viscometry and ¹⁹F NMR studies show that the PS‐block‐PEO copolymers, in contrast to their matching PS‐block‐PEO‐R_F copolymers, exhibit a micellar rather than the associative behavior seen for the latter. However, the presence of an excess of fluorinated acid, used for end‐functionalization, produces a reduction of the associative behavior above the overlap concentration, with the fluorinated acid acting like a surfactant. A competition may also occur between PS—and R_F—mediated micellization. Copyright © 2004 Society of Chemical Industry