In-situ preparation of poly(2-hydroxyethyl methacrylate)-titania hybrids using γ-radiation

Hybrids of titania and poly(2-hydroxyethyl methacrylate) were prepared using ⁶⁰Co γ-radiation initiated polymerisation combined with sol-gel chemistry of titanium isopropoxide. Careful control of the rates of the sol-gel reaction was achieved with acetylacetone which ensured that the dispersion of titania nanoparticles remained stable and minimised aggregation during the polymerisation reaction. Essentially quantitative conversion was achieved with extremely few residual volatiles, as indicated by evolved gas FTIR and solid state NMR. The process yielded transparent orange hybrids, with titania loadings ranging from 3 wt.% to 15 wt.% (TGA). The pyrolysis onset temperatures increased by approximately 30 °C for the hybrids compared to the unfilled polymer. DSC indicated higher T_g’s compared with other pHEMA data in the literature, with a decrease in magnitude of the T_g occurring with increasing titania content. TEM shows high dispersion of particles in the 10-20 nm range, with modest aggregation. Equilibrium swelling showed that the hybrid hydrogels swelled less than half that of unfilled polymer, indicating that the titania is restricting the mobility of the chains through a cross-linking process.     

Synthesis of cobalt complexes and their evaluation as an adhesion promoter in a rubber–steel wire system

Cobalt adhesion promoters are considered as one of the most important ingredients in the tyre industry for adhesion between the rubber compound and the brass plated steel cord for manufacturing of steel-belted radial tyres. Most of the commercially available cobalt compounds are either higher fatty acid salts, or cobaltchelate complexes, e.g., cobalt octate, naphthenate, stearate and cobalt-boron complexes. Among all the available cobalt salts, cobalt-boron complexes are the most popular ones and bond well. Considering the availability, economics and performance of the different cobalt salts, an attempt has been made in this study to synthesise different cobalt-chelate complexes and to make a comparative evaluation. In some of the cases the cobalt complexes developed showed better adhesion properties as compared to the control compound.     

Diffusion of an adhesion promoter (chlorinated polypropylene) into polypropylene/ethylene–propylene copolymer (PP/EP) blends: method of quantification

The adhesion between an organic coating and a polymer substrate may depend on the diffusion of organic coating constituents into the substrate. The diffusion of chlorinated polypropylene (CPO) into polymer substrates was quantified by using radiolabelled CPO and monitoring its dissolution subsequent to its application. The CPO was ³H-radiolabelled by reduction with NaB³H₄ in tetrahydrofuran. The characterization of native and labelled CPO by size exclusion chromatography and differential scanning calorimetry showed that the reaction did not degrade the resin. Several substrates and CPO application conditions were used in order to create a wide range of CPO-substrate interfaces. The measurement of the progressive dissolution of radiolabelled CPO showed a clear-cut differentiation between the CPO bound by the substrate and the CPO simply deposited as a film, and provided a minimum estimation of the amount which was retained through macromolecular entanglement or diffusion. A larger amount of bound CPO was found in PP/EP than in PP, in agreement with a broader CPO concentration profile (several μm) at the surface of the former, as observed by ToF-SIMS imaging.     

Synthesis of poly(lactic acid)–poly(ethylene glycol) copolymers using multi-SO3H-functionalized ionic liquid as the efficient and reusable catalyst

Poly(lactic acid)–poly(ethylene glycol) copolymers were synthesized under the catalysis of multi-SO₃H-functionalized ionic liquid. Compared to the ordinary ionic liquids and the traditional Lewis acid catalysts, the ionic liquids with multi-sulfonic acid groups were more catalytically active, and the reaction conversion rate reached up to 97.8 %. The molecular weight of the resulting copolymer was 5.69 × 10⁴ g mol^?1 and the degree of crystallinity was 42.9 %. The copolymers were also of higher hydrophilicity and better mechanical properties. The reaction kinetics of copolymerization was analyzed. The intrinsically high catalytic activity of multi-SO₃H groups originated from the lower activation energy and the higher free acidity. The recovering catalytic activity of the multi-SO₃H ionic liquid catalyst was higher, suggesting that it is a recyclable, environmentally friendly catalyst.     

Effects of the lamination temperature on the properties of poly(ethylene terephthalate-co-isophthalate) in polyester-laminated tin-free steel can — II. Adhesion mechanism of poly(ethylene terephthalate-co-isophthalate) to TFS

The adhesion strength between poly(ethylene terephthalate-co-isophthalate) (co-PET) and tin-free steel (TFS) was investigated by varying the lamination temperature using a blister test. As the lamination temperature increased, the adhesion strength increased rapidly at the beginning and then saturated. The main reason for the increase of adhesion with the lamination temperature was an improved degree of wetting. This was manifested by the fact that the variation in the degree of wetting was very similar to that of the adhesion strength. The degree of wetting was dependent on the melt viscosity of co-PET. The results of differential scanning calorimetry (DSC) and rheometrics dynamic spectrometry (RDS) showed that the high extent of the crystalline phase increased remarkably the melt viscosity of co-PET, leading to incomplete wetting. When the co-PET/TFS joint was immersed in hydrochloric acid solution, the pattern of the front penetration line and the rate of penetration of hydrochloric acid solution into the co-PET/TFS interface were different, depending on the lamination temperature and the direction of penetration. The wet adhesion strength was found to increase with increasing lamination temperature because the size of voids at the co-PET/TFS interface resulting from incomplete wetting decreased.     

Voltammetric determination of alkannin using an Au nanoparticles–poly(diallyldimethylammonium chloride)-functionalized graphene nanocomposite film

An electrochemical sensor based on Au nanoparticles (AuNPs)–poly(diallyldimethylammonium chloride) (PDDA)-functionalized graphene (AuNPs–PDDA-G) nanocomposite was fabricated for the sensitive detection of alkannin. The nanocomposite was characterized by X-ray diffraction, ultraviolet/visible spectra, scanning electron microscopy, and transmission electron microscopy. Cyclic voltammetry and differential pulse voltammetry were used to investigate the electrochemical behaviors of alkannin on the AuNPs–PDDA-G nanocomposite film-modified glassy carbon electrode. This electrochemical sensor displayed satisfactory analytical performance for alkannin detection over a range from 5.0 nmol L^?1 to 3.0 μmol L^?1 with a detection limit of 1.4 nmol L^?1 (S/N = 3). Moreover, the sensor also exhibited good reproducibility and stability, and could be used for the detection of alkannin in real samples with satisfactory results.     

Synthesis of poly(ε-caprolactone)-poly(L-lactide) block copolymers by melt or solution sequential copolymerization using nontoxic dibutylmagnesium as initiator

Summary  Poly(ε-caprolactone)-poly(L-lactide) (PCL-PLLA) block copolymers were synthesized via melt or solution sequential copolymerization of ε-caprolactone (ε-CL) and L-lactide (L-LA) using nontoxic dibutylmagnesium as initiator. The formation of block structure was confirmed by ¹H-, ¹³C NMR, GPC, and FT-IR, it can be concluded that the block copolymers PCL-PLLA have been successfully synthesized by both melt and solution sequential copolymerization methods. Two melting endothermic peaks (T_m) during heating and two crystallization exothermal peaks (T_c) during cooling were observed in DSC curves. XRD patterns of the copolymers were approximately the superposition of both the PCL and PLLA homopolymers. The results indicated the coexistence of both PCL and PLLA crystalline microdomains, and the microphase separation took place in the block copolymers.     

Preparation of methoxy poly (ethyleneglycol)-b-poly (ε-caprolactone-co-L-lactide) and characterization as biodegradable micelles

Polynorbornene-functionalized multiwalled carbon nanotubes (MWCNTs) were prepared by a “grafting from” approach, on varying the catalyst-MWCNT spacing to evaluate the influence of the starting catalyst-MWCNT distance on the polymerization efficiency. In particular, 2nd generation Grubbs catalysts and Hoveyda-Grubbs catalysts, both active in the ring opening metathesis polymerization of olefins, were grafted on MWCNTs at 8 to 12 atom spacing from the nanotube surface, and the activity of initiators was tested in the 2-norbornene polymerization. According to our results, initiator performances depend (i) on the length of the arm connecting the catalyst to the MWCNTs, being initiators with longer arms more efficient, and (ii) on the class of Ru catalysts, being Hoveyda-Grubbs catalysts surprisingly more active at room temperatures than 2nd generation Grubbs catalysts. High fractions (80–95 wt%) of polymer covalently bound to the nanotubes in the MWCNT-grafted polynobornene obtained composites were achieved.     

Surface treatments of wood–plastic composites (WPCs) to improve adhesion

In an effort to improve the adhesive bonding between wood–plastic composites (WPCs) formulated with polypropylene and a commercial epoxy adhesive, surface treatments were performed to chemically and/or physically modify the surface of WPCs. The treatments were performed on extruded WPC that had been planed and consisted of chromic acid treatment, flame treatment, water treatment, flame then water treatment and water then flame treatment. The strength of the adhesive bonds of the treated samples was tested following ASTM D 905 and the maximum shear stress was calculated for each treatment. The chromic acid and flame treatments increased their respective average shear strengths by 97% and 67% compared to an untreated control group. The increase in bond strength due to these two treatments is believed to be a result of their oxidative mechanisms. The water treatment, which consisted of covering the planed surface of a WPC with water for 10 min, resulted in an increase in shear strength of 31% relative to the control. Characterization of the water-treated WPC surface with profilometry and scanning electron microscopy indicated that the likely mechanism for the increase in bond strength was the absorption of water and subsequent swelling of the wood present in the WPC, creating greater surface area for bonding. The combination of flame and water treatments showed increased shear strength relative to the individual treatments alone, indicating that the two processes might act synergistically to facilitate the formation of stronger adhesive bonds.     

pH- and temperature-sensitive semi-interpenetrating network hydrogels composed of poly(acrylamide) and poly(γ-glutamic acid) as amoxicillin controlled-release system

Hydrogels of semi-interpenetrating networks composed of poly(acrylamide) (PAAm) and poly(γ-glutamic acid) (γ-PGA) with different proportions were studied as potential amoxicillin controlled-release devices. The effects of the hydrogels composition, pH, and temperature on the kinetics and final release of amoxicillin were determined in batch experiments. The release kinetic tests were conducted using a buffer solution as the release medium under pH conditions of 3 and 7.2, and temperature of 25, 37, and 45 °C. The final percentage of amoxicillin released from the hydrogels was found to increase with temperature, pH, and the amount of γ-PGA in the hydrogels formulation. Overall, equilibrium conditions in the kinetics experiments were achieved within 240 min of hydrogel–solution contact. The overall rate of amoxicillin release was represented with a two-parameter empirical model as a function of time.     

Diffusion of adhesion promoter (CPO) into polypropylene/ethylene–propylene (PP/EP) copolymer blends: mechanism

Chlorinated polypropylene (CPO) is commonly used as an adhesion promoter for paint on polypropylene/ ethylene-propylene copolymer blends (PP/EP). An adhesion mechanism frequently proposed in the literature is the CPO diffusion into the substrate, leading to molecular entanglement. It is shown here that CPO and PP/EP are immiscible. On the other hand, the use of radiolabelled CPO allowed quantification of CPO diffusion into PP/EP substrates as a function of several parameters and under conditions which simulate industrial practice. Diffusion requires substrate swelling by the solvent. This explains that it increases with the EP content of the material, with the solvent ability to swell the substrate, and with the thickness of the paint. For baked samples, diffusion passes through a maximum when the delay between CPO application and baking is varied. This is due to a balance between two processes working in opposite directions, i.e. substrate swelling and solvent evaporation.     

Mechanism of thermal generation of poly(p-phenylene vinylene) from poly(p-xylene-α-dimethylsulphonium halides)

The thermal conversion of poly(p-xylene-α-dimethylsulphonium halides) into poly(p-phenylene vinylene) (PPV) can occur through two concomitant reactions. The principal reaction is an elimination of dimethyl sulphide and halogen acid, while the second reaction, an undesirable one, is the nucleophilic attack of the halide counterion on a methyl group to form the methyl halide and a methyl sulphide. The two thermal processes were observed in the pyrolysis of both poly(p-xylene-α-dimethylsulphonium bromide) and poly(p-xylene-α-dimethylsulphonium chloride). On storage at room temperature, poly(p-xylene-α-dimethylsulphonium halides) undergo partial decomposition to PPV, as shown by thermogravimetric experiments. The flash pyrolysis-gas chromatography-mass spectrometry of PPV obtained by the thermal conversion of poly(p-xylene-α-dimethylsulphonium bromide) at 400°C was also investigated.     

Effect of immobilization of poly(γ-glutamic acid) on the biocompatibility of electrospun poly (L-lactide) mats

In this study, poly(L-lactide) (PLLA) non-woven mats were prepared by electrospinning technique, followed by treating with oxygen plasma and grafting with 3-aminopropyl triethoxysilane (APTES), then immersed in poly(γ-glutamic acid) (γ-PGA) solution to form a layer of γ-PGA on the surface. In so doing, hydrophobic PLLA would become highly hydrophilic. Through characterization of hydrophilicity and biocompatibility, the feasibility of these modified mats for wound dressing was evaluated. The results show that after the grafting of γ-PGA, the swelling ratio increased greatly from 7% for pristine PLLA mat to 321% for γ-PGA-grafted PLLA mat, and the contact angle decreased from 112° to 25°. In vitro cytocompatibility tests against L929 fibroblast show that γ-PGA-grafted PLLA was non-cytotoxic. In addition, the proliferation of fibroblasts was higher on γ-PGA-grafted PLLA than on pristine PLLA.     

Fabrication of transparent γ-AlON by direct 2-step pressureless sintering of Al2O3 and AlN using an AlN-deficient composition

Transparent polycrystalline aluminum oxynitride (γ-AlON) was fabricated by the pressureless two-step sintering of α-Al₂O₃ and AlN after adding a small amount of MgO and Y₂O₃. The process was based on two assumptions. The first was the utilization of AlN-deficient non-stoichiometric composition to increase the cationic vacancies and the second was the selection of the 1st step sintering temperature that suppresses the formation of γ-AlON phase to achieve a high density after the 2nd sintering step. The 1st and 2nd sintering steps were performed at 1610–1650 and 1940–1990 °C, respectively, for 10 h in a 2.5 atmospheric nitrogen pressure, and the optimal sintering conditions were determined. The fabricated γ-AlON showed a mean grain size of 164–248 μm without the presence of significant scattering centers, where the sample prepared using an optimal condition revealed a very high transmittance of 84.7% along with comparable mechanical properties.     

Multiarm star with poly(ethyleneimine) core and poly(ε-caprolactone) arms as modifiers of diglycidylether of bisphenol A thermosets cured by 1-methylimidazole

Well-defined multiarm star copolymers, with hyperbranched poly(ethyleneimine) (PEI) as the core and poly(ε-caprolactone) (PCL) arms with different degree of polymerization were synthesized by cationic ring-opening polymerization of ε-caprolactone from a hyperbranched poly(ethyleneimine) core and used to modify diglycidylether of bisphenol A formulations cured with 1-methylimidazole as anionic initiator. The curing process was studied by dynamic scanning calorimetry (DSC) and FTIR. By rheometry the complex viscosity of the multiarm stars synthesized and the influence of their addition to the reactive mixture was analyzed in detail. The resulting materials were characterized by thermal and mechanical tests. The addition of the multiarm star to the formulation led to homogeneous materials with a slightly toughened fracture in comparison to neat DGEBA thermosets without compromising thermal characteristics.     

Synthesis of organo-functionalized nanosilica via a co-condensation modification using γ-aminopropyltriethoxysilane (APTES)

An easy and swift pathway in preparation of organo-functionalized silica in nanosize range with amine-terminated group via co-condensation method is reported. The process is a self-catalyzed reaction by amine group of organosilane without the addition of ammonia as a catalyst at room temperature. A modified nanosilica with particle size of ～60 nm, highly monodispersed and low aggregation was successfully produced. The use of methanol as a solvent leads to the increase in particle size. CHN, FTIR and NMR analyses revealed the presence of organo-functional group in the bulk and at the surface of the silica particles.     

Compatibilizing capability of poly(β-hydroxybutyrate-,co-ε-caprolactone) in the blend of poly(β-hydroxybutyrate) and poly(ε-caprolactone)

In order to increase the miscibility in the blend of poly(β-hydroxybutyrate) [PHB] and poly(ε-caprolactone) [PCL], PHB/PCL copolyesters were used as compatibilizers. These PHB/PCL copolyesters were synthesized by transesterification in solution phase. The melting point [T_m] depression, which was not observed in PHB/PCL blend without compatibilizer, was observed when PHB/PCL copolyesters as compatibilizers were added to the PHB/PCL blend system. As the amount of compatibilizer added to the blend increased, the crystallization temperature [T_c] of PCL in the blend increased and T_c of PHB in the blend decreased. The difference in T_c between PHB and PCL was gradually reduced. When the sequence length of PHB block and PCL block in the PHB/PCL copolyester increased, the miscibility of the blend increased. This is evidenced by the depression in the T_m of PHB and PCL in the blend and by the decrease in the difference of T_c between PHB and PCL. From the polarizing optical micrographs, the phase separation in PHB/PCL blend was observed. However, in the presence of PHB/PCL copolyester, the spherulite of PHB grows in equilibrium with one phase melt. Received: 27 July 1998/Revised version: 12 October 1998/Accepted: 4 November 1998     

Synthesis of Polypeptide-Polyether Conjugates from an Activated Urethane Derivative of γ-Benzyl-L-glutamate as a Monomer

N-(4-Nitrophenoxycarbonyl)-γ-benzyl-L-glutamate (1) was heated at 60 °C in N,N-dimethylacetoamide (DMAc) in the presence of p-(tert-butyl)phenylmethylamine (2) to afford poly(γ-benzyl-L-glutamate) in high yield. ¹H NMR analysis of the obtained polymer revealed that the p-(tert-butyl)phenylmethyl group was successfully introduced into the polymer chain end. Under the same conditions, polycondensations of 1 in the presence of poly(ethylene glycol)s having amino terminals were performed. Both of the components were consumed quantitatively to afford the corresponding block copolymers having poly(γ-benzyl-L-glutamate) and poly(ethylene glycol) segments. The molecular weights of the copolymers were controlled by the feed ratio [1]₀/[amino group in the macroinitiator]₀. Electronic Supplementary Material  The online version of this article at contains supplementary material, which is available to authorized users.     

Crystallization and morphology of poly(ethylene succinate) and poly(β-hydroxybutyrate) blends

Summary The melting and crystallization behavior of poly(β-hydroxybutyrate) (PHB) and poly(ethylene succinate) blends has been studied by differential scanning calorimetry and optical microscopy. The results indicate that PHB and PES are miscible in the melt. Consequently the blend exhibits a depression of the melting temperature of both PHB and PES. In addition, a depression of the equilibrium melting temperature of PHB is observed. The Flory-Huggins interaction parameter (χ₁₂ ), obtained from melting point depression data, is composition dependent, and its value is always negative. Isothermal crystallization in the miscible blend system PES/PHB is examined by polarized optical microscope. The presence of the PES component gives a wide variety of morphologies. The spherulites exhibit a banded structure and the band spacing decreases with increase PES content. Received: 29 June 1998/Revised version: 31 August 1998/Accepted: 10 September 1998