• Title/Summary/Keyword: syndiotacticity

Search Result 13, Processing Time 0.019 seconds

Critical Syndiotacticity Required for In-Situ Fibrillation of Poly(vinyl Alcohol) during Saponification of Poly(vinyl Ester)

  • Lyoo, Won-Seok;John Blackwell
    • Proceedings of the Korean Fiber Society Conference
    • /
    • 1998.04a
    • /
    • pp.130-134
    • /
    • 1998
  • The physical properties of poly(vinyl alcohol) (PVA) are highly dependent on the degree of syndiotacticity, which is determined primarily by the choice of the vinyl ester monomer precursor. Efforts to produce more syndiotactic PVAs, as well to increase the molecular weight, have centered on the polymerization of vinyl trifluoroacetate,$^1$ vinyl trichloroacetate,$^2$ and vinyl pivalate (VPi).(omitted)

  • PDF

Cd(II) and Zn(II) Complexes Containing N,N'-Bidentate N-(Pyridin-2-ylmethylene)cyclopentanamine: Synthesis, Characterisation and Methyl Methacrylate Polymerisation

  • Song, Yujin;Kim, Dongil;Lee, Ha-Jin;Lee, Hyosun
    • Bulletin of the Korean Chemical Society
    • /
    • v.35 no.10
    • /
    • pp.2929-2934
    • /
    • 2014
  • The reaction between $[CdBr_2{\cdot}4H_2O]$ and anhydrous $[ZnCl_2]$ with N,N'-bidentate N-(pyridin-2-ylmethylene)-cyclopentanamine (impy) in ethanol yields dimeric $[(impy)Cd({\mu}-Br)Br]_2$ and monomeric $[(impy)ZnCl_2]$ complexes, respectively. The X-ray crystal structure of Cd(II) and Zn(II) complexes revealed that the cadmium atom in $[(impy)Cd({\mu}-Br)Br]_2$ and zinc in $[(impy)ZnCl_2]$ formed a distorted trigonal-bipyramidal and tetrahedral geometry, respectively. Both complexes showed moderate catalytic activity for the polymerisation of methyl methacrylate (MMA) in the presence of modified methylaluminoxane (MMAO), with polymethylmethacrylate (PMMA) syndiotacticity of about 0.70.

Influence of the Syndiotacticity of Poly(vinyl alcohol) block on the formation of micelles for Poly(vinyl alcohol-b-styrene) (Poly(vinyl alcohol) block의 신디오탁틱이 Poly(vinyl alcohol-b-styrene)의 micelle형성에 미치는 영향)

  • 이광화;조창기
    • Proceedings of the Korean Fiber Society Conference
    • /
    • 2003.04a
    • /
    • pp.291-292
    • /
    • 2003
  • Amphiphilic block copolymer는 self-assembly특성을 가지고 있기 때문에 선택된 용매 속에서 nanoscale-domain 즉 micelle을 형성할 수 있다. 이러한 특성은 기타 불용성 물질을 가용화하고 colloidal particle을 안정화시키거나 micro-emulsion을 형성할 수 있어 pharmaceutics, drug delivery system등 영역, 그리고 emulsion stabilizer, thickener, dispersion agent등으로 사용될 수 있다. (중략)

  • PDF

Preparation of Syndiotacticity-Rich Ultrahigh Molecular Weight Poly(vinyl alcohol) with High Yield Using Low Temperature Suspension Polymerization of Vinyl Pivalate (피발산비닐의 저온 현탁중합에 의한 고교대배열 초고분자량 폴리비닐알코올의 고효율 제조)

  • 류원석;박찬식
    • Proceedings of the Korean Fiber Society Conference
    • /
    • 2002.04a
    • /
    • pp.33-36
    • /
    • 2002
  • 폴리비닐알코올 (poly(vinyl alcohol), PVA)은 의류 및 산업용 섬유, 막, 약물전달, 암세포 괴사용 색전제등에 널리 사용되고 있다[1,2]. 이런 PVA와 같은 비닐계 고분자는 분자량 이외에도 입체규칙성에 따라 그 물리적 성질이 변화하는데 그 입체규칙성에 따라 혼성배열, 동일배열 및 교대배열 고분자로 분류할 수 있다. PVA는 일반적으로 55% 이상의 교대배열 다이애드기 함량을 가질 때 교대배열 PVA라고 불린다. (중략)

  • PDF

Preparation of Water-Soluble Syndiotacticity-Rich Low Molecular Weight Poly(vinyl alcohol) by Solution Copolymerization of Vinyl Pivalate/Vinyl Acetate in Tetrahydrofuran and Saponification (피발산비닐과 아세트산비닐의 테트라히드로푸란계 용액공중합에 의한 수용성 저분자량 교대배열 폴리비닐알코올의 제조)

  • Lyo, Won-Seok;Yeum, Jeong-Hyun;Ji, Byung-Chul
    • Proceedings of the Korean Fiber Society Conference
    • /
    • 2002.04a
    • /
    • pp.187-190
    • /
    • 2002
  • Poly(vinyl alcohol) (PVA) is a representative hydrophilic and water-soluble polymer and widely employed in various applications such as fibers for clothes and industries, films, membranes, medicines for drug delivery system, and cancer cell-killing embolic materials. Moreover, PVA fibers, gels, and films are potentially high-performance materials because they have high tensile and impact strengths, high tensile modulus, high abrasion resistance, excellent alkali resistance, and oxygen barrier property which are superior to those of any known polymers[1,2]. (omitted)

  • PDF

Effect of Stereoregularity on the Properties of Syndiotacticity-Rich Ultrahigh Molecular Weight Poly(vinyl alcohol)/Dimethylsu1foxide/Water Gel

  • Park, Jin-Hyun;Lyoo, Won-Seok;Ko, Sohk-Won
    • Proceedings of the Korean Fiber Society Conference
    • /
    • 1998.10a
    • /
    • pp.13-16
    • /
    • 1998
  • Poly(vinyl alcohol) (PVA) gels are easily formed via physical pathway. Most PVA solutions including PVA/water solution are well known to form thermally reversible gels at low temperature but these gels showed poor mechanical properties. In order to overcome this weak point, transparent crosslinked PVA hydrogels were prepared by electron beam irradiation or by chemical process with crosslinking agents or additives. (omitted)

  • PDF

Preparation of Poly(vinyl pivalate/vinyl acetate) Microspheres Using Suspension Copolymerization of Vinyl Pivalate and Vinyl Acetate and its characterization (피발산비닐과 아세트산비닐의 현탁공중합을 이용한 폴리(피발산비닐/아세트산비닐) 입자의 제조 및 특성)

  • Park, Chan-Sik;Kim, Joon-Ho;Lyoo, Won-Seok
    • Proceedings of the Korean Fiber Society Conference
    • /
    • 2003.10b
    • /
    • pp.46-48
    • /
    • 2003
  • Poly(vinyl alcohol) (PVA) obtained from PVPi has the highest syndiotacticity among (PVA)s obtained via radical polymerization, and the s-diad content of PVA prepared by low temperature polymerization of vinyl pivalate (VPi)[1-5] comes to eve. 60%, Therefore, we an obtain (PVA)s with various tacticities through the copolymerization of vinyl acetate (VAc) and VPi and can examine the relation between physical properties of (PVA)s and their tacticities. (omitted)

  • PDF