Synthesis and thermal properties of poly(acrylonitrile‐co‐allyl glycidyl ether)‐graft‐methoxypoly(ethylene glycol) copolymers as novel solid–solid phase‐change materials for thermal energy storage

We synthesized a series of poly(acrylonitrile‐co‐allyl glycidyl ether)‐graft‐methoxypoly(ethylene glycol) (PAA‐g‐MPEG) copolymers as novel polymeric solid–solid phase‐change materials by grafting methoxypoly(ethylene glycol) (MPEG) to the main chain of poly(acrylonitrile‐co‐allyl glycidyl ether) (PAA). PAA was the skeleton, and MPEG was a functional side chain, which stored and released heat during its phase‐transition process. Fourier transform infrared spectroscopy and ¹H‐NMR spectroscopy analysis were performed to investigate the chemical structures. The crystalline morphology and crystal structures were also measured with polarized optical microscopy and X‐ray diffraction. Moreover, the thermal‐energy‐storage properties, thermal stability, and thermal reliability of the PAA‐g‐MPEG copolymers were characterized by differential scanning calorimetry and thermogravimetric analysis (TGA) methods. These analysis results indicate that the MPEG chains were successfully grafted onto PAA, and we found that the PAA‐g‐MPEG copolymers had typical solid–solid phase‐transition temperatures in the range 11–54 °C and high latent heat enthalpies between 44 and 85 J/g. In addition, the as‐prepared PAA‐g‐MPEG copolymers showed reusability and thermal reliability, as shown by the thermal cycle testing and TGA curves. Therefore, the synthesized PAA‐g‐MPEG copolymers have considerable potential for thermal energy storage. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46641.     

Synthesis of pH‐responsive crosslinked poly[styrene‐co‐(maleic sodium anhydride)] and cellulose composite hydrogel nanofibers by electrospinning

BACKGROUND: Stimuli‐sensitive materials show enormous potential in the development of drug delivery systems. But the low response rate of most stimuli‐sensitive materials limits their wider application. We propose that electrospinning, a technique for the preparation of ultrafine fibrous materials with ultrafine diameters, may be used to prepare materials with a fast response to stimuli. RESULTS: Poly[styrene‐co‐(maleic sodium anhydride)] and cellulose (SMA‐Na/cellulose) hydrogel nanofibers were prepared through hydrolysis of precursor electrospun poly[styrene‐co‐(maleic anhydride)]/cellulose acetate (SMA/CA) nanofibers. In the presence of diethylene glycol, the SMA/CA composite nanofibers were crosslinked by esterification at 145 °C, and then hydrolyzed to yield crosslinked SMA‐Na/cellulose hydrogel nanofibers. These nanofibers showed better mechanical strengths and were pH responsive. Their water swelling ratio showed a characteristic two‐step increase at pH = 5.0 and 8.2, with the water swelling ratio reaching a maximum of 27.6 g g^?1 at pH = 9.1. CONCLUSION: The crosslinked SMA‐Na hydrogel nanofibers supported on cellulose showed improved dimensional stability upon immersion in aqueous solutions. They were pH responsive. This new type of hydrogel nanofiber is a potential material for biomedical applications. Copyright © 2009 Society of Chemical Industry     

Design and electrical conductivity of poly(acrylic acid‐g‐gelatin)/graphite conducting gel

A novel poly(acrylic acid‐g‐gelatin)/graphite composite is synthesized by aqueous solution polymerization. Based on the electrical conductivity of graphite nanoplatelets and the absorbency of poly(acrylic acid‐g‐gelatin)/graphite, a novel conducting gel with a conductivity of 3.18 mS cm^?1 is prepared. The effects of synthesis parameters on the electrical conductivity of the gels are investigated in detail. An appended network structure model of the poly(acrylic acid‐g‐gelatin)/graphite conducting gel is proposed. The conducting gel presents a high mechanical strength in cyclohexane, which is important for the gel applications. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Preparation and characterization of thermally conductive polystyrene/carbon nanotubes composites

Thermally conductive polystyrene (PS)/multi‐walled carbon nanotubes (MWNTs) nanocomposites was prepared through a simple solution‐evaporation method assisted by ultrasonic irradiation. To enhance the dispersion of MWNTs in PS, MWNTs were chemically functionalized with poly(styrene‐co‐maleic anhydride) (SMA) (MWNT‐g‐SMA), which had benzene group and exhibited strong affinity with PS. The thermal conductive properties of PS increased and the mechanical properties decreased in presence of MWNTs, while by addition of MWNT‐g‐SMA, the properties of the composites can be improved to some extent. The thermal conductivity can reach 0.89 W/m K for the composite with 33.3 vol % MWNT‐g‐SMA, which was four times higher than that of neat PS. A linear increase of the thermal conductivity was observed with increasing MWNTs‐g‐SMA content, and the Maxwell–Eucken model and the Agari model were used for theoretical evaluation. Compared with MWNT‐OH, MWNT‐g‐SMA with larger diameter exhibited diffused boundary with the PS matrix, resulting from the strong interfacial bonding of the two phases. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Studies of adsorption of alkaline trypsin by poly(methacrylic acid) brushes on chitosan membranes

Poly(methacrylic acid)‐grafted chitosan membranes (chitosan‐g‐poly(MAA)) were prepared in two sequential steps: in the first step, chitosan membranes were prepared by phase‐inversion technique and then epichlorohydrin was used as crosslinking agent to increase its chemical stability in acidic media; in the second step, the graftcopolymerization of methacrylic acid onto the chitosan membranes was initiated by ammonium persulfate (APS) under nitrogen atmosphere. The chitosan‐g‐poly(MAA) membranes were first used as an ion‐exchange support for adsorption of trypsin from aqueous solution. The influence of pH, equilibrium time, ionic strength, and initial trypsin concentration on the adsorption capacity of the chitosan‐g‐poly(MAA) membranes have been investigated in a batch system. Maximum trypsin adsorption onto chitosan‐g‐poly(MAA) membrane was found to be 92.86 mg mL^?1 at pH 7.0. The experimental equilibrium data obtained for trypsin adsorption onto chitosan‐g‐poly(MAA) membranes fitted well to the Langmuir isotherm model. The adsorption data was analyzed using the first‐ and second‐order kinetic models, and the experimental data was well described by the second‐order equation. More than 97% of the adsorbed trypsin was desorbed using glutamic acid solution (0.5M, pH 4.0). In addition, the chitosan‐g‐ poly(MAA) membrane prepared in this work showed promising potential for various biotechnological applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and characterization of anionic graft copolymers containing poly(ethylene oxide) grafts

Graft copolymers containing poly(ethylene oxide) side chain attached to maleic anhydride‐alt‐vinyl methyl ether (MA‐VME) copolymer were prepared by coupling MA‐VME and poly(ethylene glycol) monomethyl ether (MPEG) by esterification in DMF at 90°C. MPEG and dodecyl alcohol (DA) were grafted onto MA‐VME copolymer in o‐xylene at 140°C in the presence of p‐toluene sulfonic acid as catalyst. The molecular weights of MPEG were found to influence the rate of the grafting reaction and the final degree of conversion. The graft copolymers were characterized by IR, GPC, and ¹H‐NMR. DSC was used to examine thermal properties of the graft copolymers. The analysis indicates that grafts have phase‐separated morphology with the backbone and the MPEG grafts forming separate phases. The properties in aqueous solutions of these grafts were studied with respect to aggregation behavior and viscometric properties. In aqueous solution, the polymers exhibited polyelectrolyte behavior (i.e., a dramatic increase of the viscosity upon neutralization). Graft copolymers with DA have lower viscosities. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1138–1148, 2002     

High‐performance biosourced poly(lactic acid)/polyamide 11 blends with controlled salami structure

High‐performance biosourced poly(l ‐lactide) (PLLA)/polyamide 11 (PA11) (55/45) blends with small amounts of rubber, ethylene glycidyl methacrylate‐graft‐styrene‐co‐acrylonitrile (EGMA‐g‐AS), were fabricated by simple melt compounding. Epoxide groups in EGMA‐g‐AS are ready to react with both PA11 and PLLA, and thus EGMA‐g‐AS could be manipulated to locate mainly in either PA11 phase or PLLA phase by variation of the blending sequence. It was found that the blend with salami structure in which EGMA‐g‐AS is predominantly dispersed in the PLLA phase provides not only significantly improved tensile ductility, but also excellent film impact strength, while keeping relatively high modulus. The elongation at break and the film impact strength of such materials with 6 phr EGMA‐g‐AS are 322% and 361 kJ m^?2, which are 78 and 5.2 times those of unmodified PLLA, respectively. In contrast, the blends with EGMA‐g‐AS mainly in the PA11 phase fracture in a brittle mode with low toughness. The toughening mechanism of the PLLA/PA11 blends with the sub‐inclusion salami structure was investigated using a double‐notch technique. The brittle‐to‐tough transition was observed on increasing the rubber sub‐inclusion concentration in the PLLA phase. © 2013 Society of Chemical Industry     

Potent Triple Helix Stabilization by 5′,3′‐Modified Triplex‐Forming Oligonucleotides

Anthraquinone and pyrene analogues attached to the 3′ and/or 5′ termini of triplex‐forming oligonucleotides (TFOs) by various linkers increased the stability of parallel triple helices. The modifications are simple to synthesize and can be introduced during standard solid‐phase oligonucleotide synthesis. Potent triplex stability was achieved by using doubly modified TFOs, which in the most favourable cases gave an increase in melting temperature of 30 °C over the unmodified counterparts and maintained their selectivity for the correct target duplex. Such TFOs can produce triplexes with melting temperatures of 40 °C at pH 7 even though they do not contain any triplexstabilizing base analogues. These studies have implications for the design of triplex‐forming oligonucleotides for use in biology and nanotechnology.     

Properties and preparation of olefin block copolymer/thermoplastic polyurethane blends

The properties of olefin block copolymer (OBC)/thermoplastic polyurethane (TPU) blends with or without maleic anhydride (MA) modification were characterized and compared. Compared with the OBC/TPU blends, OBC‐g‐MA/TPU blends displayed finer morphology and reduced domain size in the dispersed phase. The crystallization temperatures of TPU decreased significantly from 155.9 °C (OBC/TPU) to 117.5 °C (OBC‐g‐MA/TPU) at low TPU composition in the blends, indicating the inhibition of crystallization through the sufficient interaction of modified OBC with TPU composition. The modified systems showed higher thermal stability than the unmodified systems over the investigated temperature range due to the enhanced interaction through inter‐bonding. The highest improvement in tensile strength was more than fivefold for OBC‐g‐MA/TPU (50/50) in comparison with its unmodified blend via the enhanced interfacial interaction between OBC‐g‐MA and TPU. This also led to the highest Young's modulus of 77.8 ± 3.9 MPa, about twofold increase, among the investigated blend systems. A corresponding improvement on the ductility was also observed for modified blends. The modification did not vary the glass transition temperature and crystalline structure much, thus the improvement in the mechanical properties was mainly attributed to the improved compatibility and interaction from the compatibilization effect as well as increased viscosity from the crosslinking effect for modified blends. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43703.     

Effective methodology for the production of novel nanocomposite films based on poly(vinyl chloride) and zinc oxide nanoparticles modified with green poly(vinyl alcohol)

Ultrasonic irradiation and solution dispersion methods were used to organize transparent worthwhile poly(vinyl chloride) (PVC) nanocomposite (NC) films which contain different amounts of modified zinc oxide nanoparticles (NP)s. First, modification of ZnO NPs was accomplished by biocompatible poly(vinyl alcohol) (PVA) to increase NCs compatibility and dispersity in the PVC matrix. The investigation followed by the fabrication and characterization of PVC/ZnO‐PVA NCs which obtained via fast and facile ultrasonication irradiation. The measurements of X‐ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy were used for the characterization of properties, structure and morphology of the obtained NPs and their NCs. Furthermore, thermal and optical properties of the resulting NCs were also carried out by thermogravimetric analysis, ultraviolet‐visible transmission, and absorption spectra. Morphology results demonstrate well‐dispersed characteristics of ZnO‐PVA NPs incorporated in the PVC matrix which resulted from modification. Also, modified ZnO NPs enhanced mechanical properties of prepared NC films. Prepared NCs could be categorized as self‐extinguishing materials on the basis of the limiting oxygen index values. POLYM. COMPOS., 38:1800–1809, 2017. © 2015 Society of Plastics Engineers     

Poly(methyl methacrylate)‐grafted cellulose nanocrystals: One‐step synthesis,nanocomposite preparation,and characterization

Cellulose nanocrystals (CNCs) are ideal reinforcing agents for polymer nanocomposites because they are lightweight and nano‐sized with a large aspect ratio and high elastic modulus. To overcome the poor compatibility of hydrophilic CNCs in non‐polar composite matrices, we grafted poly(methyl methacrylate) (PMMA) from the surface of CNCs using an aqueous, one‐pot, free radical polymerization method with ceric ammonium nitrate as the initiator. The hybrid nanoparticles were characterized by CP/MAS NMR, X‐ray photoelectron spectroscopy, infrared spectroscopy, contact angle, thermogravimetric analysis, X‐ray diffraction, and atomic force microscopy. Spectroscopy demonstrates that 0.11 g/g (11 wt %) PMMA is grafted from the CNC surface, giving PMMA‐g‐CNCs, which are similar in size and crystallinity to unmodified CNCs but have an onset of thermal degradation 45 °C lower. Nanocomposites were prepared by compounding unmodified CNCs and PMMA‐g‐CNCs (0.0025–0.02 g/g (0.25–2 wt %) loading) with PMMA using melt mixing and wet ball milling. CNCs improved the performance of melt‐mixed nanocomposites at 0.02 g/g (2 wt %) loading compared to the PMMA control, while lower loadings of CNCs and all loadings of PMMA‐g‐CNCs did not. The difference in Young's modulus between unmodified CNC and polymer‐grafted CNC composites was generally insignificant. Overall, ball‐milled composites had inferior mechanical and rheological properties compared to melt‐mixed composites. Scanning electron microscopy showed aggregation in the samples with CNCs, but more pronounced aggregation with PMMA‐g‐CNCs. Despite improving interfacial compatibility between the nanoparticles and the matrix, the effect of PMMA‐g‐CNC aggregation and decreased thermal stability dominated the composite performance.     

Enhancement of the antibacterial activity of natural rubber latex foam by the incorporation of zinc oxide nanoparticles

The synthesis and characterization of ZnO‐nanoparticle‐incorporated natural rubber latex foam (NRLF) are described in this article. ZnO nanoparticles were added as the primary gelling agent by the replacement of the microsized ZnO particles, whereas the control sample of the NRLF was made without the addition of any ZnO particles. ZnO nanopowder was evaluated by X‐ray diffraction (XRD), whereas the aqueous dispersion of nano‐ZnO was evaluated by transmission electron microscopy (TEM) micrograph analysis. The modified NRLF materials were evaluated by scanning electron microscopy (SEM)–energy‐dispersive X‐ray (EDX) analysis and XRD analysis. The antibacterial activities of the modified NRLF samples were evaluated quantitatively and qualitatively by antibacterial susceptibility tests against Gram‐positive Staphylococcus aureus and Gram‐negative Escherichia coli bacteria. We found that the XRD peaks matched perfectly with reference code 98‐002‐6593, which was the hexagonal phase. The particle sizes given by TEM image analysis were less than 60 nm. Most of the XRD peaks obtained for the modified NRLF matched with that of the ZnO nanopowder; this proved the presence of nano‐ZnO in the modified NRLF. Further, it was proven by SEM and EDX analysis. The NRLF modified by nanosized ZnO inhibited the growth of the so‐called bacteria in a very strong manner. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39601.     

Improved synthesis of a branched poly(ethylene imine)‐modified cellulose‐based adsorbent for removal and recovery of Cu(II) from aqueous solution

This study focuses on an improved synthesis of a branched poly (ethylene imine) (PEI)‐modified cellulose‐based adsorbent (Cell‐g‐PGMA‐PEI). We aim to improve the adsorbent capacity by reducing side reaction of epoxide ring opening during graft copolymerization of glycidyl methacrylate (GMA) onto cellulose which increases the content of epoxy groups, anchors to immobilize branched PEI moieties. FTIR spectra provided the evidence of successful graft copolymerization of GMA onto cellulose initiated by benzoyl peroxide (BPO) and modification with PEI. The amount of epoxy groups of Cell‐g‐PGMA was 4.35 mmol g^?1 by epoxy titration. Subsequently, the adsorption behavior of Cu(II) on cell‐g‐PGMA‐PEI in aqueous solution has been investigated. The data from the adsorption kinetic experiments agreed well with pseudo‐second‐order model. The adsorption isotherms can be interpreted by the Langmuir model with the maximum adsorption capacity of 102 mg g^?1 which was largely improved compared with the similar adsorbent reported. The dynamic adsorption capacity obtained from the column tests was 119 mg g^?1 and the adsorbent could be regenerated by HCl of 0.1 mol L^?1. Results indicate that the novel pathway for the synthesis of Cell‐g‐PGMA‐PEI exhibits significant potential to improve the performance of adsorbents in removal and recovery of Cu(II) from aqueous solution. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Lipophilic 2′‐O‐Acetal Ester RNAs: Synthesis,Thermal Duplex Stability,Nuclease Resistance,Cellular Uptake,and siRNA Activity after Spontaneous Naked Delivery

The in vivo application of siRNA depends on its cellular uptake and intracellular release, and this is an unsatisfactorily resolved technical hurdle in medicinal applications. Promising concepts directed towards providing efficient cellular and intracellular delivery include lipophilic chemical modification of siRNA. Here we describe chemistry for the production of modified siRNAs designed to display improved transmembrane transport into human cells while preserving the potency of the RNAi‐based inhibitors. We report the synthesis and the biochemical and biophysical characteristics of 2′‐O‐phenylisobutyryloxymethyl (PiBuOM)‐modified siRNAs and their impact on biological activity. In the case of spontaneous cellular uptake of naked PiBuOM‐modified siRNA, we observed increased target suppression in human cells relative to unmodified or pivaloyloxymethyl (PivOM)‐modified siRNA. We provide evidence of improved spontaneous cellular uptake of naked PiBuOM‐modified siRNA and of substantial target suppression in human cells in serum‐containing medium.     

Synthesis and phase separation of poly(N‐isopropyl acrylamide‐co‐methoxy polyethyleneglycol monomethacrylate)

The poly(N‐isopropyl acrylamide‐co‐methoxy polyethyleneglycol monomethacrylate, NIPAM‐co‐MPEG) with different length of ethylene oxide (EO) were synthesized from their monomers, NIPAM and MPEGs. The numbers of repeating units of EO were 6, 10, 24, and 46. The chemical structure and mole ratio of the monomers was determined by Fourier transform infrared (FTIR), ¹H‐NMR, and ¹³C‐NMR spectroscopy. The d‐spacing increased with the number of EO and the values of the copolymers were in the range of 0.437–0.452 nm. The lower critical solution temperature of the poly(NIPAM‐co‐MPEG) shifted to higher temperature as the number of EO and the amount of MPEG increased. The change of chemical shift for methoxy proton in MPEG exhibited a larger than those of the other protons of the poly(NIPAM‐co10?2MPEG). Activation energy (E_a) for methoxy proton in MPEG showed a larger value than that of the methyl proton in NIPAM. These NMR results indicate the fact that more significant conformational transformations occur in the methoxy group through the phase separation than in the methyl group in NIPAM. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1833–1841, 2006     

Interfacial modification of high impact polystyrene magnesium hydroxide composites effects on flame retardancy properties

High impact polystyrene (HIPS)/magnesium hydroxide (MH) composites were prepared by melt‐blending. Two kinds of interfacial modifiers were used in this research, maleinated poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS‐g‐MA) triblock copolymer and PS. The effects of the use levels of SEBS‐g‐MA on the flame retardancy of HIPS/elastomer/MH based on unmodified and PS‐modified surface were investigated by TEM, FTIR, and combustion tests (horizontal burning test and cone calorimetry). The combustion results showed that comparing composites containing unmodified MH, the flame retarding properties of composites containing PS‐modified MH were obviously improved. The increased performance can be explained that the PS covered on the surface of MH could further improve dispersion of the filler in matrix. Furthermore, there existed a critical thickness of interfacial boundary for optimum flame‐retarding properties in both ternary composites based MH and PS‐modified MH. When the interfacial boundary relative thickness is less than 0.53, the introduction of SEBS‐g‐MA can improve the dispersion degree, leading the improvement of flame retardancy properties. However, with the increase of interfacial boundary thickness, the SEBS‐g‐MA coating around MH acted as a heat and mass transfer barrier, leading to the reduction of flame retardancy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of diblock copolymers consisting of methoxy poly(ethylene glycol) and poly(ε‐caprolactone)/poly(L‐lactide) and their degradation property

Methoxy poly(ethylene glycol)‐b‐poly(ε‐caprolactone) (MPEG‐PCL) or MPEG‐b‐poly(L ‐lactide) (MPEG‐PLLA) diblock copolymers were prepared by the polymerization of CL or LA, using MPEG as an initiator in the presence of stannous octoate. MPEG‐b‐poly(ε‐caprolactone‐ran‐L ‐lactide) (MPEG‐PCLA) diblock copolymers with different chemical composition of PCL and PLLA were also prepared by adjusting the amount of CL and LA from MPEG in the presence of stannous octoate. In degradation study, the degradation of the MPEG‐PCLA diblock copolymers mainly depends on the PCL and PLLA segments present in their structure. MPEG‐PCLA, with intermediate ratio of PCL and PLLA segment, completely degraded after 14 weeks. Meanwhile, partially degraded MPEG‐PCLA segments and parent MPEG segments were observed at higher PCL or PLLA segment contents. Introduction of PLLA into the PCL segments caused a lowering of the crystallinity of the diblock copolymers, thus, inducing a faster incoming of water into the copolymers. We confirmed that the diblock copolymers, with lower degree of crystallinity, have degraded more rapidly. POLYM. ENG. SCI., 46: 1242–1249, 2006. © 2006 Society of Plastics Engineers     

Facile and controllable synthesis of hybrid silica nanoparticles densely grafted with poly(ethylene glycol)

We report that a mixture of good and poor solvents greatly enhances the grafting density of nanosized silica grafted with poly(ethylene glycol) (PEG ) by the ‘grafting to’ method. Methoxypolyethylene glycol (MPEG ) (molecular weight 750, 2000 and 4000 g mol^?1) was modified in a controlled manner to prepare epoxide terminated PEG (MPEG‐EO ). Silica nanoparticles were modified with N ‐(2‐aminoethy)‐3‐aminopropylmethyldimethoxysilane through the silanization coupling reaction to obtain a well‐defined siloxane structure. MPEG‐EO was coupled to the modified silica by the reaction of their terminal groups in a mixed solvent (n ‐decane/toluene). The grafting density of MPEG‐EO was found to be controlled by the concentration of MPEG‐EO and the ratio of n ‐decane to toluene in the grafting system. Based on TGA , the maximum grafting density was found to be about 2.8, 1.47 and 0.76 chains nm^?2 for molecular weights of 750, 2000 and 4000, respectively, which is extremely high compared to previous reports. This high grafting density can be explained by the decreased chain dimension of PEG in the presence of the poor solvent. The method can be applied to other nanoparticles and polymers which can greatly enhance the application of SiO₂ nanocomposites. © 2017 Society of Chemical Industry     

Preparation and dynamic mechanical properties of poly(styrene‐b‐butadiene)‐modified clay nanocomposites

Polybutyl acrylate (PBA) was intercalated into clay by the method of multistep exchange reactions and diffusion polymerization. The clay interlayer surface is modified, and obtaining the modified clay. The structures of the clay‐PBA, clay‐GA (glutamic acid), and the clay‐DMSO (dimethyl sulfoxide) were characterized using X‐ray diffraction (XRD). The new hybrid nanocomposite thermoplastic elastomers were prepared by the clay‐PBA with poly(styrene‐b‐butadiene) block copolymer (SBS) through direct melt intercalation. The dynamic mechanical analysis (DMA) curves of the SBS/modified clay nanocomposites show that partial polystyrene segments of the SBS have intercalated into the modified clay interlayer and exhibited a new glass transition at about 157°C (T_g3). The glass transition temperature of polybutadiene segments (T_g1) and polystyrene segments out of the modified clay interlayer (T_g2) are about ?76 and 94°C, respectively, comparied with about ?79 and 100°C of the neat SBS, and they are basically unchanged. The T_g2 intensity of the SBS‐modified clay decreases with increasing the amounts of the modified clay, and the T_g3 intensity of the SBS‐modified clay decreases with increasing the amounts of the modified clay up to about 8.0 wt %. When the contents of the modified clay are less than about 8.0 wt %, the SBS‐modified clay nanocomposites are homogeneous and transparent. The T_gb and T_gs of the SBS‐clay (mass ratio = 98.0/2.0) are ?78.39 and 98.29°C, respectively. This result shows that the unmodified clay does not essentially affect the T_gb and T_gs of the SBS, and no interactions occur between the SBS and the unmodified clay. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1499–1503, 2002; DOI 10.1002/app.10353     

Phase Transfer Mediated Self-Assembly of CdTe–Polymer Nanohybrids for Uniform Fluorescent Films

We report an available strategy for fabricating CdTe nanocrystal–polymer nanohybrids by using poly(methylmethacrylate-co-dimethyl diallyl ammonium chloride) (poly(MMA-co-DMDAAC)) as polymer matrix via a phase transfer process. CdTe nanocrystals (NCs) were firstly prepared via the thio-aqueous synthetic approach. Also prepared were the poly(MMA-co-DMDAAC) copolymers via free radical polymerization in organic phase. Then the as-prepared CdTe NCs were completely transferred from water to the chloroform phase under the direction of the poly(MMA-co-DMDAAC) copolymers due to electrostatic interactions between the positively charged amino group of the copolymer and the negatively charged ligand on the surface of NCs, resulting in the formation of CdTe-poly(MMA-co-DMDAAC) nanohybrids. Interestingly, the NC–polymer nanohybrids showed highly enhanced photoluminescence (PL) properties in comparison with that of the parent TGA-stabilized CdTe NCs. The uniform fluorescent films of such NC–polymer nanohybrids were further successfully fabricated to exhibit excellent PL properties and thermal stability, which might be useful in optoelectronic applications.