Doug-Youn Lee

Soochow University (PRC), Suzhou, Jiangsu Sheng, China

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Publications (12)11.02 Total impact

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    ABSTRACT: Stability of the styrene miniemulsion costabilized by carboxylated polyurethane resins was investigated. The shelf life and the droplet size were measured. The results show that styrene miniemulsion costabilized by carboxylated polyurethane can be prepared although it is not as efficient as is hexadecane. The shelf life of the miniemulsion is influenced by the amount of the polyurethane and sodium dodecyl sulfate. The alkaline condition and the smaller molecular weight of the polyurethane are in favor of the stability of the miniemulsion. The polymerization results show that the hydrophility of the particle or droplet surface plays an important role in the process of the nucleation and polymerization. Homogeneous nucleation and droplet nucleation coexist in these systems. Nucleation lasts to 40–60% conversion of the monomer in the acid medium, but it continues until the end of the polymerization in the alkaline medium. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1933–1940, 2003
    Journal of Applied Polymer Science 01/2003; 87(12):1933 - 1940. · 1.40 Impact Factor
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    ABSTRACT: The effect of interfacial crosslinking on miscibility behavior in blend systems of isocyanate-functionalized poly(Bu methacrylate) (PBMA) and a carboxylic alkali-sol. resin, poly(styrene/α-methylstyrene/acrylic acid) (SAA), was studied with different di-Me m-isopropenylbenzyl isocyanate (TMI) concns. For the blend films of pure PBMA and SAA, both theor. anal. and direct observation showed immiscibility between PBMA and SAA. For the blend systems of isocyanated PBMA and SAA, Fourier transform IR spectra and gel permeation chromatog. analyses qual. showed the crosslinking between the isocyanate group in isocyanated PBMA and the carboxylic group in SAA. Two tan δ peaks were shown in the blend system of SAA and isocyanated PBMA contg. low concns. of TMI (from 0 to 5 wt %), and the span of the two peaks became shorter as the TMI concn. increased. For a high TMI concn. (7 wt %), only one tan δ peaks was obsd. This result means the interfacial crosslinking between isocyanated PBMA and SAA occurred fully, and thus the miscibility between two polymers was significantly improved. As these results showed, the tensile strength of the blend film of isocyanated PBMA and SAA was higher than that of pure PBMA and SAA. [on SciFinder(R)]
    Journal of Applied Polymer Science 01/2003; 90(3):792-798. · 1.40 Impact Factor
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    ABSTRACT: A styrene miniemulsion was prepd. using carboxylated polyurethane as the sole costabilizer and sodium dodecyl sulfate as the surfactant. The effects of the amt. of carboxylated polyurethane, the amt. of the initiator and surfactant, the presence of a water-phase inhibitor (sodium nitrite), and the reaction temp. on the kinetics of the miniemulsion polymn. were investigated. The evolution of the particle size during the polymn. was measured. The results show that the polymn. rate was proportional to the 0.21 power of the surfactant concn. and the 0.30 power of azobisisobutyronitrile. The droplet nucleation and homogeneous nucleation were found to be coexistent in the polymn. The hydrophilicity of the particle surface plays a key role in the nucleation of the particle and, therefore, has an important effect on the kinetics of the polymn. [on SciFinder(R)]
    Journal of Applied Polymer Science 01/2003; 87(12):1941-1947. · 1.40 Impact Factor
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    ABSTRACT: The effects of miscibility enhancement between polystyrene (PS) and poly(ethylene-co-acrylic acid) (EAA) on dynamic mech. properties, barrier property, and tensile strength were investigated. Ethylene-modified latexes were prepd. by the emulsion polymn. of styrene using EAA, [Mn: 18 800; acid no.: 140], as a polymeric emulsifier. The EAA-grafted-PS in-situ-formed during the emulsion polymn. lead to the improvement of miscibility between PS and EAA. The dynamic mech. properties of the ethylene-modified PS films exhibited a single glass transition temp. (Tg) value, thus conforming to the law of miscibility. The grafted and anchoring EAA mols. onto PS particles resulted in significant increase of chem. resistance. Addnl., the tensile strength property was improved for the ethylene-modified PS system due to the enhanced compatibility between PS and EAA, compared with simple blends. [on SciFinder(R)]
    Colloids and Surfaces A Physicochemical and Engineering Aspects 01/2002; 207(1-3):155-160. · 2.11 Impact Factor
  • Journal of Applied Polymer Science - J APPL POLYM SCI. 01/2001; 79(3):479-487.
  • Macromolecular Symposia 01/2000; 151(1):479-485.
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    ABSTRACT: Free-radical terpolymn. of α-methylstyrene/styrene/acrylic acid (AMS/ST/AA) in a continuous stirred tank reactor (CSTR) was studied theor. and exptl. A series of reactions were conducted to investigate the effect of the reaction temp., residence time, solvent contents, initiator concn., chain-transfer agent level, and different monomer compns. on the mol. wt. distribution (MWD). The math. model based on "the instantaneous property method (IPM)" and the pseudokinetic rate const. method was introduced and modified to predict the MWD of the bulk terpolymer produced in a CSTR. The effects of process variables were included in the math. model. Extensive comparisons were made between the theor. results and exptl. values. The rate of the free-radical terpolymn. of AMS/ST/AA was comparatively slow and it was found that the concn. of α-methylstyrene had a strong influence on the mol. wt. and polydispersity of the MWD. This presumably reflected the existence of a normal biomol. termination rate and a slow propagation rate due to steric hindrances at the doubly substituted vinyl carbon atom or transfer of the allylic hydrogen from the α-Me group. Good agreement was obtained between calcd. MWD and the exptl. one by assuming that the disproportionation termination of free radicals was the dominant chain-stoppage mechanism. [on SciFinder(R)]
    Journal of Applied Polymer Science 01/2000; 79(3):479-487. · 1.40 Impact Factor
  • Jin-Sup Shin, Doug-Youn Lee, Jung-Hyun Kim
    Macromolecular Symposia 01/2000; 151(1):509-514.
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    ABSTRACT: The effect of alkali-soluble resin (ASR) postadded to emulsifier-free monodisperse poly(n-butyl methacrylate) latexes (PBMA) on the surface properties of the latex films formed was investigated using the contact angle method. The contact angles of a probe liquid (containing 50:50 wt % ethylene glycol and water) on the film surface were determined as a function of the annealing temperature of the film and the annealing duration. The ASR, poly(styrene/α-methylstyrene/acrylic acid), was found to exude to the air/polymer interface after annealing, as monitored using FTIR−ATR. Thus the surface properties of the films were dependent on the concentration of the ASR employed, the annealing temperature, and the duration. Annealing the film at a temperature approximately equal to the Tg of ASR allows them (ASR) to undergo unrestricted migration to the film surface and also to expose the hydrophobic region of their chains to the surface. The more hydrophobic character of the film annealed at 150 °C with a higher contact angle as compared to that at 50 °C is a result of the change in chain conformation of the ASR at the surface brought about by annealing. Also, the results illustrate that the hydrophobic−hydrophilic character of the PBMA−SAA film surface can be changed readily by merely adjusting the annealing temperature.
    Langmuir. 12/1999; 16(4).
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    ABSTRACT: The film morphology of emulsifier-free poly(n-butyl methacrylate) (PBMA) latex in the presence of post-added alkali-soluble resin (ASR) was studied using atomic force microscopy (AFM). The film morphology was monitored, from the nascent stage after water was evaporated from the dispersion, as a function of annealing temperature and its duration. The AFM results suggest strongly the formation of a hard shell of ASR, namely poly(styrene/alpha-methylstyrene/acrylic acid) (SAA) over the soft PBMA particle. During annealing, the incompatibility of the two polymers leads to the migration and accumulation of SAA at the interstices and interfacial regions among the arrays of PBMA particles, and also at the film surface. The hard shell of SAA retards the diffusion of the PBMA molecules across the particle/particle interface and slows down the gradual coalescence of film formation. Annealing at high temperature ruptures the SAA shells and the PBMA particles interdiffuse at a faster rate than the SAA due to its lower Tg compared to that of SAA. The difference in the rates of fusion of the SAA and PBMA phases leads to the formation of indentations on individual particles at high annealing temperature and long annealing duration. The occurrence of this feature increases with the annealing temperature and its duration. These indentations are eventually transformed into ‘depressions’ on the latex films when the indentations at the top of the individual particles sag inwords at sufficiently high annealing temperature and long annealing time. The surface enrichment of SAA is confirmed by the results of fainer transform infrared spectroscopy with attenuated internal reflectance of the film surface. Copyright © 1999 John Wiley & Sons, Ltd.
    Surface and Interface Analysis 01/1999; 28(1):28-35. · 1.22 Impact Factor
  • Doug-Youn Lee, Jung-Hyun Kim, Tae-Ik Min
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    ABSTRACT: Alkali-soluble random copolymer (ASR), poly(styrene/alpha-methylstyrene/acrylic acid) was used as a polymeric emulsifier in the emulsion polymerization of styrene and methyl methacrylate, respectively. ASR could form aggregates like micelles and the solubilization ability of the aggregates was dependent on the neutralization degree of ASR. The rate of polymerization of styrene decreased as the neutralization degree of ASR was increased with little change in particle size. This result can be explained by the solubilization ability of ASR aggregate and the entry rate of radicals into the particle. As the degree of neutralization of ASR increased, the ASR aggregate was less efficient in solubilizing the monomer, and it was more difficult for radicals to enter the particle through the extended ASR layer on the particle surface, which led to a decrease in the rate of polymerization. The polystyrene (PS) latexes prepared using ASR showed the monodispersed particle size distribution. On the other hand, the particle size distribution of poly(methyl methacrylate) (PMMA) latexes became broader as the neutralization of ASR increased. This could be explained by the effects of the water solubility of the monomer and the neutralization degree of ASR on particle formation.
    Colloids and Surfaces A Physicochemical and Engineering Aspects 01/1999; 153(1):89-97. · 2.11 Impact Factor
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    ABSTRACT: The effects of alkali-soluble resin containing carboxylated random copolymers on the film structure and individual particle morphology of poly(n-butyl methacrylate) latex film have been studied using atomic force microscopy. More instances of disruption to regular packing of the particles in the latex film, e.g., vacancies, cracking, and dislocations in the regular arrays and domains of random arrangement of particles, were observed in the poly(n-butyl methacrylate) latex film containing alkali-soluble resin than in its absence. In addition, indentations of the tops of the individual latex particles on the film surface were observed. The extent of this occurrence increased with the concentration of the alkali-soluble resin, the annealing temperature, and its duration. The results were interpreted in terms of the different degree of fusion of the poly(n-butyl methacrylate) particles and layer of alkali-soluble resin adsorbed on them during the film formation process.
    Langmuir. 09/1998; 14(19).