The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform

Yong Huang - One of the best experts on this subject based on the ideXlab platform.

  • self assembly of Ethyl Cellulose graft polystyrene copolymers in acetone
    Polymer, 2009
    Co-Authors: Yanxiang Li, Dawa Shen, Hongliang Kang, Min Wu, Yong Huang
    Abstract:

    Abstract The self-assembly of the dense graft copolymers Ethyl Cellulose-graft-polystyrene (EC-g-PS) in acetone was investigated by using dynamic light scattering (DLS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). It was found that EC-g-PS copolymers can self-assemble into spherical micelles in acetone. The micelles' size increases with increasing the copolymer concentration and the PS side-chain length. Moreover, the copolymers can self-assemble into multimolecular micelles at relatively high polymer concentration while unimolecular micelles can be formed at low concentration. The micelles have a core–shell structure with the Ethyl Cellulose main chains in the shell and the side polystyrene chains in the core of the micelles.

  • synthesis of amphiphilic Ethyl Cellulose grafting poly acrylic acid copolymers and their self assembly morphologies in water
    Polymer, 2006
    Co-Authors: Hongliang Kang, Dawa Shen, Benqiao He, Yong Huang
    Abstract:

    Abstract Amphiphilic Ethyl Cellulose (EC)- g -poly(acrylic acid) (PAA) copolymers were synthesized by atom transfer radical polymerization (ATRP). Firstly, Ethyl Cellulose macro-initiators with the degree of the 2-bromoisobutyryl substitution of 0.04 and 0.25 synthesized by the esterification of the hydroxyl groups remained in EC macromolecular chains and the 2-bromoisobutyryl bromides. Secondly, tert -butyl acrylate was polymerized by ATRP with the Ethyl Cellulose macro-initiator and EC- g -P t BA copolymers were prepared. Finally, the EC- g -PAA copolymers were prepared by hydrolyzing tert -butyl group of the EC- g -P t BA copolymers. The grafting copolymers were characterized by means of GPC, 1 H NMR and FTIR spectroscopies. The molecular weight of graft copolymers increased during the polymerization and the polydispersity was low. A kinetic study showed that the polymerization was first-order. Meanwhile, EC- g -PAA copolymers were self-assembled to micelles or particles with diameters of 5 nm and 100 nm in water (pH = 10) when the concentration was 1.0 mg/ml.

  • densely grafting copolymers of Ethyl Cellulose through atom transfer radical polymerization
    Journal of Polymer Science Part A, 2005
    Co-Authors: Dawa Shen, Hui Yu, Yong Huang
    Abstract:

    Densely grafting copolymers of Ethyl Cellulose with polystyrene and poly (mEthyl methacrylate) were synthesized through atom transfer radical polymerization (ATRP). First, the residual hydroxyl groups on the Ethyl Cellulose reacted with 2-bro- moisobutyrylbromide to yield 2-bromoisobutyryloxy groups, known to be an efficient initiator for ATRP. Subsequently, the functional Ethyl Cellulose was used as a macroi- nitiator in the ATRP of mEthyl methacrylate and styrene in toluene in conjunction with CuBr/N,N,N 0 ,N@,N@-pentamEthyldiEthylenetriamine as a catalyst system. The molecular weight of the graft copolymers increased without any trace of the macroini- tiator, and the polydispersity was narrow. The molecular weight of the side chains increased with the monomer conversion. A kinetic study indicated that the polymer- ization was first-order. The morphology of the densely grafted copolymer in solution was characterized through laser light scattering. The individual densely grafted copolymer molecules were observed through atomic force microscopy, which confirmed the synthesis of the densely grafted copolymer. V C 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4099-4108, 2005

  • The synthesis and thermotropic behaviour of an Ethyl Cellulose derivative containing azobenzene-based mesogenic moieties
    Liquid Crystals, 2003
    Co-Authors: Changcheng Wu, Yong Huang, Qincui Gu, Shouxi Chen
    Abstract:

    An Ethyl Cellulose derivative containing azobenzene-based mesogenic moieties was prepared by the reaction of 4-methoxyazobenzene-4′-oxyacetic acid and Ethyl Cellulose by esterification in the presence of N,N′ -dicylcohexylcarbodiimide and 4-dimEthylaminopyridine. Its chemical structure and liquid crystalline properties were characterized by FTIR, 1H NMR, POM, DSC and WAXD. The degree of substitution of the Cellulose backbone by the azobenzene-based mesogenic moieties is 0.9. The polymer is thermotropic and exhibits liquid crystalline behaviour over the temperature range 125–172°C.

  • The synthesis and thermotropic liquid crystalline behavior of mesogenic moiety-linked Ethyl Cellulose
    Polymer Bulletin, 2002
    Co-Authors: Changcheng Wu, Yong Huang, Shouxi Chen
    Abstract:

    In this paper, a new mesogenic moiety was synthesized and characterized by IR, NMR, and MS. The mesogenic moiety-linked Ethyl Cellulose derivative was prepared by reaction of 4-mEthyloxyphenyl-4-oxyaceticacid benzoate with Ethyl Cellulose [EC, degree of substitution (DS) 2.1] through esterification. The polymer was characterized by IR, NMR, DSC, and hot-stage coupled polarizing microscopy. The DS of mesogenic unit is 0.49. The mesogenic moiety-linked Ethyl Cellulose derivative showed a thermotropic liquid crystalline behavior.

Catarina M M Duarte - One of the best experts on this subject based on the ideXlab platform.

  • preparation of Ethyl Cellulose mEthyl Cellulose blends by supercritical antisolvent precipitation
    International Journal of Pharmaceutics, 2006
    Co-Authors: Ana Rita C Duarte, M.d. Gordillo, Margarida M Cardoso, Ana Luisa Simplicio, Catarina M M Duarte
    Abstract:

    Abstract The supercritical antisolvent (SAS) technique was used to prepare Ethyl Cellulose/mEthyl Cellulose blends, two biocompatible polymers commonly used as drug carriers in controlled delivery systems. Ethyl Cellulose is widely used as a drug carrier. The drug release of the delivery devices can be controlled to some extent by addition of a water-soluble or water swellable polymer, such as mEthyl Cellulose. This leads to the solubility enhancement of poorly water-soluble molecules. SAS experiments were carried out at different operational conditions and microspheres with mean diameters ranging from 5 to 30 μm were obtained. The effect of CO 2 and liquid flow, temperature and pressure on particle size and particle size distribution was evaluated. The microspheres were precipitated from a mixture of dichloromethane (DCM) and dimEthylsulfoxide (DMSO) (4:1 ratio). The best process conditions for this mixture were according to our study 40 °C and 80 bar.

Ana Rita C Duarte - One of the best experts on this subject based on the ideXlab platform.

  • preparation of Ethyl Cellulose mEthyl Cellulose blends by supercritical antisolvent precipitation
    International Journal of Pharmaceutics, 2006
    Co-Authors: Ana Rita C Duarte, M.d. Gordillo, Margarida M Cardoso, Ana Luisa Simplicio, Catarina M M Duarte
    Abstract:

    Abstract The supercritical antisolvent (SAS) technique was used to prepare Ethyl Cellulose/mEthyl Cellulose blends, two biocompatible polymers commonly used as drug carriers in controlled delivery systems. Ethyl Cellulose is widely used as a drug carrier. The drug release of the delivery devices can be controlled to some extent by addition of a water-soluble or water swellable polymer, such as mEthyl Cellulose. This leads to the solubility enhancement of poorly water-soluble molecules. SAS experiments were carried out at different operational conditions and microspheres with mean diameters ranging from 5 to 30 μm were obtained. The effect of CO 2 and liquid flow, temperature and pressure on particle size and particle size distribution was evaluated. The microspheres were precipitated from a mixture of dichloromethane (DCM) and dimEthylsulfoxide (DMSO) (4:1 ratio). The best process conditions for this mixture were according to our study 40 °C and 80 bar.

Dawa Shen - One of the best experts on this subject based on the ideXlab platform.

  • self assembly of Ethyl Cellulose graft polystyrene copolymers in acetone
    Polymer, 2009
    Co-Authors: Yanxiang Li, Dawa Shen, Hongliang Kang, Min Wu, Yong Huang
    Abstract:

    Abstract The self-assembly of the dense graft copolymers Ethyl Cellulose-graft-polystyrene (EC-g-PS) in acetone was investigated by using dynamic light scattering (DLS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). It was found that EC-g-PS copolymers can self-assemble into spherical micelles in acetone. The micelles' size increases with increasing the copolymer concentration and the PS side-chain length. Moreover, the copolymers can self-assemble into multimolecular micelles at relatively high polymer concentration while unimolecular micelles can be formed at low concentration. The micelles have a core–shell structure with the Ethyl Cellulose main chains in the shell and the side polystyrene chains in the core of the micelles.

  • synthesis of amphiphilic Ethyl Cellulose grafting poly acrylic acid copolymers and their self assembly morphologies in water
    Polymer, 2006
    Co-Authors: Hongliang Kang, Dawa Shen, Benqiao He, Yong Huang
    Abstract:

    Abstract Amphiphilic Ethyl Cellulose (EC)- g -poly(acrylic acid) (PAA) copolymers were synthesized by atom transfer radical polymerization (ATRP). Firstly, Ethyl Cellulose macro-initiators with the degree of the 2-bromoisobutyryl substitution of 0.04 and 0.25 synthesized by the esterification of the hydroxyl groups remained in EC macromolecular chains and the 2-bromoisobutyryl bromides. Secondly, tert -butyl acrylate was polymerized by ATRP with the Ethyl Cellulose macro-initiator and EC- g -P t BA copolymers were prepared. Finally, the EC- g -PAA copolymers were prepared by hydrolyzing tert -butyl group of the EC- g -P t BA copolymers. The grafting copolymers were characterized by means of GPC, 1 H NMR and FTIR spectroscopies. The molecular weight of graft copolymers increased during the polymerization and the polydispersity was low. A kinetic study showed that the polymerization was first-order. Meanwhile, EC- g -PAA copolymers were self-assembled to micelles or particles with diameters of 5 nm and 100 nm in water (pH = 10) when the concentration was 1.0 mg/ml.

  • densely grafting copolymers of Ethyl Cellulose through atom transfer radical polymerization
    Journal of Polymer Science Part A, 2005
    Co-Authors: Dawa Shen, Hui Yu, Yong Huang
    Abstract:

    Densely grafting copolymers of Ethyl Cellulose with polystyrene and poly (mEthyl methacrylate) were synthesized through atom transfer radical polymerization (ATRP). First, the residual hydroxyl groups on the Ethyl Cellulose reacted with 2-bro- moisobutyrylbromide to yield 2-bromoisobutyryloxy groups, known to be an efficient initiator for ATRP. Subsequently, the functional Ethyl Cellulose was used as a macroi- nitiator in the ATRP of mEthyl methacrylate and styrene in toluene in conjunction with CuBr/N,N,N 0 ,N@,N@-pentamEthyldiEthylenetriamine as a catalyst system. The molecular weight of the graft copolymers increased without any trace of the macroini- tiator, and the polydispersity was narrow. The molecular weight of the side chains increased with the monomer conversion. A kinetic study indicated that the polymer- ization was first-order. The morphology of the densely grafted copolymer in solution was characterized through laser light scattering. The individual densely grafted copolymer molecules were observed through atomic force microscopy, which confirmed the synthesis of the densely grafted copolymer. V C 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4099-4108, 2005

Ana Luisa Simplicio - One of the best experts on this subject based on the ideXlab platform.

  • preparation of Ethyl Cellulose mEthyl Cellulose blends by supercritical antisolvent precipitation
    International Journal of Pharmaceutics, 2006
    Co-Authors: Ana Rita C Duarte, M.d. Gordillo, Margarida M Cardoso, Ana Luisa Simplicio, Catarina M M Duarte
    Abstract:

    Abstract The supercritical antisolvent (SAS) technique was used to prepare Ethyl Cellulose/mEthyl Cellulose blends, two biocompatible polymers commonly used as drug carriers in controlled delivery systems. Ethyl Cellulose is widely used as a drug carrier. The drug release of the delivery devices can be controlled to some extent by addition of a water-soluble or water swellable polymer, such as mEthyl Cellulose. This leads to the solubility enhancement of poorly water-soluble molecules. SAS experiments were carried out at different operational conditions and microspheres with mean diameters ranging from 5 to 30 μm were obtained. The effect of CO 2 and liquid flow, temperature and pressure on particle size and particle size distribution was evaluated. The microspheres were precipitated from a mixture of dichloromethane (DCM) and dimEthylsulfoxide (DMSO) (4:1 ratio). The best process conditions for this mixture were according to our study 40 °C and 80 bar.