Si-Tae Noh

Synthesis of high molecular weight poly(styrene-b-methyl methacrylate) using a plug flow reactor system by anionic polymerization

AbstractSequential anionic polymerizations of styrene and methyl methacrylate and 2-vinylpyridine in tetrahydrofuran (THF) were conducted in a plug flow reactor system with a static mixer. Polymers [polystyrene (PS), Mn: 120×103 g·mol−1, Mw/Mn: 1.08), poly(methyl methacrylate) (PMMA, Mn: 28×103 g·mol−1, Mw/Mn: 1.09), poly(2-vinylpyridine) (P2VP, Mn: 53×103 g·mol−1, Mw/Mn: 1.08), and PS-b-PMMA (Mn: 117×103 g·mol−1, Mw/Mn: 1.12)] with a precisely controlled high molecular weight were obtained using a 1,1-diphenylhexyllithium initiator in a plug flow reactor system. PS-b-PMMA, PMMA, and P2VP were obtained in the presence of LiCl. The molecular weight distribution, which was related to the mixing efficiency of the static mixer, decreased with increasing flow rate. Additionally, the molecular weight of the polymers could be adjusted by varying the flow rates.

Poly(methyl methacrylate) toughened by core–shell impact modifier: Applicability of rheological equation of state

A simple rheological equation of state was developed to describe the steady-state shear viscosity of poly(methyl methacrylate) (PMMA) toughened by core–shell impact modifier. The suggested equation was successfully able to describe and predict viscosity of toughened PMMA as a function of shear rate (γ˙) and temperature.

Synthesis and thermal properties of ferrocene-modified poly(epichlorohydrin-co-2-(methoxymethyl)oxirane)

Abstract2-(Methoxymethyl)oxirane (MOMO) was used as a co-monomer for ring-opening polymerization, and four different samples of poly(epichlorohydrin-co-2-(methoxymethyl)oxirane) (poly(ECH-co-MOMO)) were synthesized by cationic ring opening copolymerization in the presence of BF3-etherate and 1,4-butandiol as an initiator system. Further, ferrocene modified copolymers were obtained by a substitution reaction of ferrocene methanol with the epichlorohydrin (ECH) unit in poly (ECH-co-MOMO) under mild conditions. Structural analysis of all products was performed using Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR). The thermal behaviors of the poly(ECH-co-MOMO) and ferrocene-modified poly(ECH-co-MOMO) were compared using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The glass transition temperatures (Tg) of PECH and PMOMO were −47 and −61 °C, respectively. As the contents of PMOMO increased, the Tg of the poly(ECH-co-MOMO)s were decreased and the onset of thermal decomposition shifted to a higher temperature. The decomposition temperature of poly(ECH-co-MOMO) was higher than that of the ferrocene-modified poly(ECH-co-MOMO).

Synthesis and characterization of poly(ferrocenyl glycidyl ether)-1,2-butylene oxide copolymers

Five different samples of poly(epichlorohydrin-co-1,2-butylene oxide) (poly(ECH-co-BO)) were synthesized by ring opening cationic copolymerization in the presence of BF3-etherate with diethyleneglycol as an initiator system. Poly(ferrocenyl glycidyl ether)-butylene oxide (poly(FcGE)-BO) copolymers were obtained by a substitution reaction of ferrocene methanol with the epichlorohydrin (ECH) unit in poly(ECH-co-BO) under basic conditions. Structural analysis of all products was performed using Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR). The thermal behaviors of the poly(ECH-co-BO) and poly(FcGE)-BO copolymers were compared using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). As iron content increased, the Tg of poly(FcGE)-BO copolymers also increased. The decomposition temperature of poly (ECH-co-BO) was higher than those of poly(FcGE)-BO copolymers.

Photopolymerization kinetic studies of UV-curable sulfur-containing difunctional acrylate monomers using photo-DSC

We synthesized UV-curable difunctional sulfur-containing thioacrylate and thiourethane acrylate with high refractive indices. The monomer structures were confirmed by nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared spectroscopy (FTIR). The photopolymerization kinetics of 3,3′-thiobis(1-(phenylthio)propane-3,2-diyl) diacrylate (SMDA) and 4,12-dioxo-6,10-bis(phenylthiomethyl)-3,13-dioxa-8-thia-5,11-diazapentadecane-1,15-diyl diacrylate (SMUA) were investigated by photo-differential scanning calorimetry (photo-DSC). The effects of various parameters such as the UV intensity, temperature, photoinitiator concentration, and the type of initiator were evaluated. In SMDA, as the temperature and light intensity increased, the peak maximum time tended to decrease. The conversion increased with increasing temperature up to 60 °C and light intensity up to 20 mW/cm2. The highest polymerization conversion was achieved with a PI concentration of 2.5% (w/w) with BK-6 as the PI. In SMUA, the rate of photopolymerization reached to the maximum value at 60 °C and 20 mW/cm2. For the PI concentration, the maximum conversion and polymerization rate constant were the highest with 2.5% (w/w). Also the highest conversion of polymerization was achieved using HP-8 as the PI. The activation energies of SMDA and SMUA were 3.95 and 36.01 kJ/mol, respectively.

On-line monitoring of reaction temperatures during anionic polymerization of poly(styrene-b-methyl methacrylate) and poly(styrene-b-2-vinyl pyridine) with a 1,1-diphenylhexyl lithium initiator in THF

Poly(styrene-b-methyl methacrylate) and poly(styrene-b-2-vinyl pyridine) block copolymers with narrow molecular weight distributions (1.05≤MWD≤1.17) were achieved via a pre-cooled monomer addition method using a diphenyl hexyl lithium initiator in tetrahydrofuran under sequential isothermal conditions. The styrene block was polymerized at −25 and −15 °C, and the second block copolymerization of PS-b-PMMA and PS-b-P2VP was carried out at −78 °C. A module-type reactor system was constructed under an inert atmosphere, which could monitor the temperature and torque during polymerization. Monomers for the second block were cooled and maintained at approximately −30 °C to control the exothermic reaction temperatures while being added to the reactor. The exothermic reaction temperature could be minimized (ΔTRMAX ≤+11 °C) by the addition of the pre-cooled monomer.