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Chun, Hyunaee,Kim, Yun-Ju,Tak, Sang-Yong,Park, Sook-Yeon,Park, Su-Jin,Oh, Chang Ho Elsevier 2018 Polymer Vol.135 No.-
<P><B>Abstract</B></P> <P>The high <I>coefficient of thermal expansion</I> (CTE) of the epoxy composite frequently causes the CTE-mismatch problem in semiconductor packaging. However, when the <I>epoxy resins available currently</I> are used for composite, the CTE-mismatch problem is inevitable even at the highly-filled conditions. In this study, the new type of bisphenol A (BPA) epoxy resin, <I>i.e., ethoxysilyl-functionalized</I> BPA epoxy was synthesized for the ultra-low CTE epoxy composite. The new epoxy composite with 85 wt% of silica content showed the ultra-low CTE of 3.2 ppm/°C and 6.0 ppm/°C at the temperature ranges of T < T<SUB>g</SUB> and T > T<SUB>g</SUB>, respectively. For comparison, the <I>non-functionalized</I> BPA epoxy composite was prepared under the similar conditions and it showed the CTE values of 8 ppm/°C and 40 ppm/°C at the temperature ranges of T < T<SUB>g</SUB> and T > T<SUB>g</SUB>, respectively. In order to understand the unique feature of the alkoxysilyl-functionalized epoxy, the reaction mechanism of the new epoxy was investigated using the model compound.</P> <P><B>Highlights</B></P> <P> <UL> <LI> New class of epoxy resin, <I>i.e,</I> alkoxysilyl-functionalized epoxy is synthesized. </LI> <LI> The epoxy composite shows the ultra-low CTE of 4.6 ppm/°C, slightly higher than wafer. </LI> <LI> The curing mechanism is studied in order to understand unique feature of new epoxy. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Chun, Hyunaee,Kim, Hyun Ah,Kim, Gyungsoo,Kim, Jaeil,Lim, Kyung-Yul Wiley Subscription Services, Inc., A Wiley Company 2007 Journal of applied polymer science Vol.106 No.4
<P>The acrylic pressure-sensitive adhesive systems with the different stress relaxation abilities are prepared by varying the curing agent from 0.3% to 3.0% and the effect of the stress relaxation ability of pressure-sensitive adhesive system on the durability of LCD polarizer was investigated. The stress relaxation ability of the crosslinked pressure-sensitive adhesive systems was measured by transient tensile test and dynamic viscoelastic test. And the durability was evaluated by the light-leakage test of polarizer coated with the pressure-sensitive adhesive after it was aged under the condition of 60°C and the relative humidity of 95% for 72 h. It was observed that the stress relaxation ability of pressure-sensitive system is decreased with the crosslinking density, as intended. And the pressure-sensitive adhesive with the lower stress relaxation ability exhibited the lower light-leakage and consequently the higher durability than the other PSA systems. This observation is obviously contradictory to the previous design strategy of PSA system and the reason for this observation was discussed briefly. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007</P>
Kim, Yun-Ju,Chun, Hyunaee,Park, Sook-Yeon,Park, Su-Jin,Oh, Chang Ho Elsevier 2018 Polymer Vol.147 No.-
<P><B>Abstract</B></P> <P>For the design of the semiconductor packaging material, one of the most important challenges is to overcome the higher thermal expansion property of ‘organic’ epoxy composite than that of the ‘inorganic’ IC chip. Therefore, in order to prepare the epoxy composite with the ultra-low coefficient of thermal expansion (CTE), the new material class of epoxy, i.e<I>., alkoxysilyl-functionalized novolac epoxy</I> (<B> <I>Si(OEt)</I> </B> <SUB> <B> <I>3</I> </B> </SUB> <B> <I>-EOCN</I> </B>) was synthesized using the ortho-cresol novolac epoxy (<B> <I>EOCN</I> </B>) as a starting material. The new epoxy composite with the 85wt% of silica showed the CTE1 (at T < Tg) of 8 ppm/°C and CTE2 (at T > Tg) of 11 ppm/°C. Note that before alkoxysilyl-modification, the CTE1 and CTE 2 of the <B> <I>EOCN</I> </B> composite were 13 ppm/°C and 44 ppm/°C, respectively. In addition, the alkoxysilyl-functionalized epoxy was observed to show the unique curing chemistry due to the participation of alkoxysilyl group in epoxy curing reaction. In order to understand the chemistry of alkoxysilyl-functionalized epoxy, the reaction mechanism was studied using the model compounds.</P> <P><B>Highlights</B></P> <P> <UL> <LI> New alkoxysilyl-functionalized novolac epoxy with low-CTE is synthesized. </LI> <LI> Curing mechanism of new epoxy is studied. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Lee, Sangkug,An, You Sun,Kim, Jae Gu,Park, In,Chun, Hyunaee,Kim, Gyungsoo,Choi, Kyung Ho American Scientific Publishers 2009 Journal of Nanoscience and Nanotechnology Vol.9 No.12
<P>Nano-sized polystyrene (PS)-silica nanocomposite particles have been prepared by soap-free emulsion polymerization using a cationic initiator, 2,2'-azobis(isobutyramidine) hydrochloride (AIBA) with a colloidal silica (Ludox SM30, 7 nm diameter). The cationic initiator leads to the formation of the PS-silica nanocomposite particles by electrostatic interaction with negatively charged silica particles. Morphology, particle size distribution, reactivity and silica content of the particles were monitored on different reaction conditions such as pH, the addition time of silica sol and the amount of the silica sol. It is found that the nucleation of styrene monomer depends on the pH of water medium, the addition time of silica, the presence of silica in polymerization system. The reaction whose styrene monomer didn't react in water medium with pH 10 was progressed in the presence of silica sol to give nanocomposite particles. In the condition of constant pH 10 in the polymerization system, the increase of the amount of silica gave little influence to the changes in the particle size and particle size distribution of nanocomposite particles. The changes in the pH of medium gave much influence on the particle size and particle size distribution due to the changes in ionic interaction of silica and initiator. The silica content absorbed on the nanocomposite particles decreases with decreasing the pH values in the polymerization media.</P>
Park, In,Ko, So Hee,An, You Sun,Choi, Kyung Ho,Chun, Hyunaee,Lee, Sangkug,Kim, Gyungsoo American Scientific Publishers 2009 Journal of Nanoscience and Nanotechnology Vol.9 No.12
<P>Monodisperse polystyrene (PS) bead particles (diameter approximately 750 nm) have been synthesized with an initiator, 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AIBA), using a surfactant-free emulsion polymerization. The PS particles charged positively by the cationic initiator exhibit uniform size with a narrow size distribution. The Stöber method was adopted to coat silica on the surface of the PS particles. The silica coatings were performed on different conditions; pH (10.0-12.5), tetraethylorthosilicate (TEOS) concentration (10-40 mM), and reaction time (1-5 h). The reaction rates are too low at low pH (10.0) so that no or little silica is coated on the PS bead particles. At high pH condition (approximately 12.5) relatively rough silica shell and heterogeneous nucleation of silica colloids were observed due to high reaction rate of TEOS hydrolysis and condensation reaction. Smooth surface with uniform thickness of silica shells were obtained at a pH value around 11. Also, the thickness of silica coated on the PS spheres increases with increase of TEOS concentration and reaction time. Silica hollow spheres were also obtained by calcination of the PS-silica core-shell particles.</P>