• Title, Summary, Keyword: Upper critical solution temperature

Search Result 12, Processing Time 0.031 seconds

Study on Initial Scattering State as a Function of Curing Temperature for Polymer Dispersed Liquid Crystal Cells with Different Mixing Ratio (고분자 분산형 액정 셀에서 혼합물의 비율에 따라 노광 온도가 초기 산란도에 미치는 영향)

  • 김미숙;서영현;이명훈;이종문;이택수;이승희
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.17 no.1
    • /
    • pp.59-64
    • /
    • 2004
  • We have fabricated the polymer dispersed liquid crystal (PDLC) cell where a control of phase separation is very important. The factors to influence the phase separation are mixing ratio of LC and polymer, curing temperature and UV intensity. In this paper, we inspected the change of a phase separation as a function of curing temperature for the mixture of E7 and. NOA65 with different ratios. When the LC concentration is less than polymer such as LC:NOA65 = 40:60wt%, the PDLC cell is influenced strongly by the curing temperature. However, when the LC concentration is much less than polymer such as LC:NOA65 = 80:20wt%, it is influenced slightly by the curing temperature. The reason is because the mixture shows upper critical solution temperature behavior and therefore it is important to know the behavior of phase separation as a function of curing temperature of the mixture.

Phase behavior of binary and ternary mixture for the poly(TBAEMA) and TBAEMA in supercritical solvents

  • Lee, Bong-Seop;Byun, Hun-Soo
    • Korean Journal of Chemical Engineering
    • /
    • v.34 no.7
    • /
    • pp.2056-2064
    • /
    • 2017
  • The cloud-point pressure of poly(t-butylaminoethyl methacrylate) [Poly(TBAEMA)] in various solvents such as supercritical carbon dioxide ($CO_2$), dimethyl ether (DME) and t-butylaminoethyl methacrylate (TBAEMA) was measured to maximum pressure and temperature of 218.79 MPa and 452.9 K, respectively. The phase behavior for the Poly(TBAEMA)+$CO_2$+TBAEMA mixture was investigated according to the various contribution factors, such as pressure, temperature and concentration with TBAEMA mass fraction of 9.9 wt%, 10.4 wt%, 14.9 wt%, 24.4 wt% and 35.2 wt%. The cloud point curves for the Poly(TBAEMA)+$CO_2$+DME (15.6-78.7 wt%) systems show the variation of the (p, T) curve from upper critical solution temperature (UCST) region to lower critical solution temperature (LCST) region as DME concentration increases. The experimental data for the $CO_2$+TBAEMA system were reported at the broad temperature range of 313.2 K to 393.2 K and the pressure range of 3.70 MPa to 20.62 MPa. The $CO_2$+TBAEMA binary system shows the type-I phase behavior with a continuous critical mixture curve, and is correlated by Peng-Robinson equation of state with the critical properties for TBAEMA obtained by Joback and Lyderson group contribution method.

Well-Defined Thermoresponsive Copolymers with Tunable LCST and UCST in Water

  • Jung, Seo-Hyun;Lee, Hyung-Il
    • Bulletin of the Korean Chemical Society
    • /
    • v.35 no.2
    • /
    • pp.501-504
    • /
    • 2014
  • A thermoresponsive polymer, poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA), was successfully synthesized by atom transfer radical polymerization (ATRP). Different amounts of 1,3-propanesultone were used as quaternization agent to transit the PDMAEMA into partially modified poly(zwitterions), resulting in p[DMAEMA-co-3-dimethyl(methacryloyloxyethyl)ammonium propanesulfonate] (PDMAEMA-co-PDMAPS). Molecular weight, molecular weight distribution, and degree of quarternization were determined by gel permeation chromatography (GPC) and 1H NMR spectroscopy. The transmission spectra of the 1.0 wt % aqueous solutions of the resulting polymers at 650 nm were measured as a function of temperature. Results showed that the lower critical solution temperature (LCST) and the upper critical solution temperature (UCST) could be easily controlled by the different composition of dimethylamino and zwitterion groups. The effect of partial quaternization on thermoresponsive properties was also studied by dynamic light scattering (DLS) with the same aqueous concentration (1.0 wt %) as employed for turbidimetry studies. The LCST and UCST values measured by DLS correlated well with those determined by turbidimetry.

Partial Miscibility of Binary Solution with Specific Interaction of Binomial Distribution (이항분포의 특정 상호작용을 갖는 이성분 용액에서의 부분혼합도)

  • Jung, Hae-Young
    • Journal of the Korean Chemical Society
    • /
    • v.58 no.6
    • /
    • pp.528-534
    • /
    • 2014
  • In some binary solution, closed miscibility loop of temperature-composition phase diagram occurs where both an upper critical solution temperature and a lower critical solution temperature exist. It is known that this phenomena occurs if specific interaction between molecules exists. There are several ways describing the specific interaction. In this work it is assumed that the total number of specific interactions is distributed according to binomial distribution. In this case, exact mathematical conditions for closed miscibility loop phase behavior are derived when the specific interaction is applied to regular solution theory, quasichemical theory and Flory-Huggins lattice theory. And we investigated the effect of parameters on the phase diagram. The phase diagram of water-nicotine is calculated and compared with experimental data.

Fabrication of a High Porous Polyethylene Membrane Using BET as a Novel Diluent (새로운 BET 희석제를 이용한 고다공성 폴리에틸렌 분리막 제조)

  • Cho, Inhyun;Lee, Soomi;Kim, Chang Keun
    • Polymer(Korea)
    • /
    • v.38 no.4
    • /
    • pp.530-534
    • /
    • 2014
  • Polyethylene (PE) membranes having various porosities are used as microfilters and separators in lithium ion batteries. Membranes having a high porosity are required for use as separators in a large scale lithium ion secondary battery. In this study, BET was examined for use as a new nontoxic diluent for the fabrication of highly porous PE membranes by thermally induced phase separation process. It was confirmed that BET can be used as a new diluent for the fabrication of the PE membranes by exploring upper critical solution temperature type phase behavior of PE mixtures with BET. When the porosity of the membrane prepared from the PE/PO mixture was compared with that prepared from PE/BET mixture, the latter was about 1.8 times higher than the former.

Thermoresponsive Phase Transitions of PLA-block-PEO-block-PLA Triblock Stereo-Copolymers in Aqueous Solution

  • Lee, Hyung-Tak;Lee, Doo-Sung
    • Macromolecular Research
    • /
    • v.10 no.6
    • /
    • pp.359-364
    • /
    • 2002
  • A series of PLA-PEO-PLA triblock stereo-copolymers with varying PLA/PEO and L-DL-LA ratios were synthesized via ring opening pelymerizations. Aqueous solutions of these copolymers undergo thermo-responsive phase transitions as the temperature monotonically increases. Further study shows that there is a critical gel concentration (CGC), and also lower and upper critical gel temperatures (CGTs), at which the thermo-responsive phase transition occurs. The CGC and CGTs are affected by various factors such as block length, as well as the compositions of the PLA blocks and of the additives. In particular, the changes in the phase diagram produced by varying the L-/DL-LA ratio in the PLA blocks were determined to be mainly due to consequent stereo-regularity changes in the PLA blocks.

Phase Behavior of Poly(methylmethacrylate) (PMMA) in Varions Solvents at High Pressure (고압상태의 다양한 용매 내에서 Poly(methylmethacrylate) (PMMA)의 상거동)

  • Kim, Je-Il;Yoo, Ki-Pung;Lim, Jong-Sung
    • Clean Technology
    • /
    • v.13 no.1
    • /
    • pp.28-33
    • /
    • 2007
  • We measured cloud points of Poly(methylmethacrylate) (PMMA) in various solvents using the high-pressure variable volume view cell apparatus. The solvents used for dissolving PMMA were chlorodifluoromethane (HCFC-22), dimethylether (DME), 1,1,1-trifluoroethane (HFC-143a), 1,1-difluoroethane (HFC-152a) and 1,1,1,2-tetrafluoroethane (HFC-134a), and the effect of $CO_2$ concentration on the phase behavior of $PMMA+HCFC-22+CO_2$ system and $PMMA+DME+CO_2$ system was observed. PMMA was dissolved well in HCFC-22 from about 340 K, 5MPa and in DME from about 300 K, 28MPa. However, PMMA was not dissolved at all up to 423.15 K, 160MPa in the other fluorine compound such as HFC-l43a, HFC-152a and HFC-134a. PMMA+HCFC-22, $PMMA+HCFC-22+CO_2$ and PMMA+DME systems exhibit the lower critical solution temperature (LCST) behavior, however, $PMMA+DME+CO_2$ system exhibits the upper critical solution temperature (UCST) behavior. In the $CO_2$ mixture, the cloud point pressure of PMMA was increased dramatically proportional to the amount of $CO_2$ added, and from this result, it was known that $CO_2$ could be used as an antisolvent for fabricating PMMA nano-particles. And the cloud point of PMMA could be controlled by changing the concentration of $CO_2$.

  • PDF

Influence of Quaternization on UCST Properties of Hydroxyl-Derivatized Polymers

  • Lee, Hyung-Il
    • Bulletin of the Korean Chemical Society
    • /
    • v.35 no.10
    • /
    • pp.3001-3004
    • /
    • 2014
  • A series of hydroxyl-derivatized quaternized polymers were successfully synthesized by atom transfer radical polymerization (ATRP) and Cu(I)-catalyzed 1,3-dipolar cycloaddition of azide and alkynes (click chemistry), followed by quaternization reactions. ATRP was employed to synthesize poly(2-hydroxyethyl methacrylate) (PHEMA), followed by introduction of alkyne groups using pentynoic acid, leading to HEMA-Alkyne. 2-Azido-1-ethanol and 3-azido-1-propanol were combined with the HEMA-Alkyne backbone via click reaction, resulting in triazole-ring containing hydroxyl-derivatized polymers. Quaternization reactions with methyl iodide were conducted on the triazole ring of each polymer. Molecular weight, molecular weight distribution, and the degree of quaternization (DQ) were determined by gel permeation chromatography (GPC) and $^1H$ NMR spectroscopy. The average molecular weight ($M_n$) of the resulting polymers ranged from $5.9{\times}10^4$ to $1.05{\times}10^5g/mol$ depending on the molecular architecture. The molecular weight distribution was low ($M_w/M_n$ = 1.26-1.38). The transmission spectra of the 0.1 wt % aqueous solutions of the resulting quaternized polymers at 650 nm were measured as a function of temperature. Results showed that the upper critical solution temperature (UCST) could be finely controlled by the level of DQ.

Miscibility of Branched Polycarbonate Blends with Poly(ethylene-co-1,4-dimethyl cyclohexane terephthalate) Copolyesters

  • Song, Jeong-Oh;Jeon, Mi-Young;Kim, Chang-Keun
    • Macromolecular Research
    • /
    • v.15 no.7
    • /
    • pp.640-645
    • /
    • 2007
  • The phase behavior of branched polycarbonate (BPC) blends with poly(ethylene terephthalate-co-1,4-dimethyl cyclohexane terephthalate) copolyesters (PECT), as well as their rheological properties, were assessed. Even though BPC blends with PECT prepared by solvent casting proved to be immiscible, BPC and PECT copolyesters containing 1,4-dimethyl cyclohexane (CHDM) from 32 to 80 mole% formed homogeneous mixtures upon heating. The homogenization temperatures of the blends decreased with increasing CHDM content in PECT. The interaction energies of the BPC-PECT pairs calculated from the phase boundary in accordance with the lattice-fluid theory were positive and also decreased with increasing CHDM content in PECT. It was shown that the phase homogenization of these blends occurs upon heating when the combinatorial entropy term, which is favorable for miscibility, overcomes unfavorable energetic terms at elevated temperatures. A novel product, which is not limited by the drawbacks of linear polycarbonate (PC) and evidences processability superior to that of the PC/PECT blends, can be developed via the blending of BPC and PECT.

Effects of Molecular Weight of Poly(4-vinylpyridine) on the Order-Disorder Transition of Molecular Bottle-brush Composed of Poly(4-vinylpyridine) and 3-Pentadecylphenol (P4VP과 PDP로 이루어진 Molecular Bottle-brush의 Order-Disorder Transition에 미치는 P4VP 분자량의 영향에 관한 연구)

  • 최종렬;조항규;전현애;노시태
    • Polymer(Korea)
    • /
    • v.24 no.4
    • /
    • pp.488-498
    • /
    • 2000
  • Molecular bottle-brush was prepared by hydrogen-bonding between poly(4-vinylpyridine)(P4VP) as main chain and 3-pentadecylphenol (PDP) as amphiphilic side chain. Variation of long period ( $L_{p}$), order-disorder transition temperature ( $T_{ODT}$) and mesomorphic structure of bottle-brush were investigated by changing various mole ratio (x) of pyridine group in P4VP and PDP and molecular weight of P4VP. Upper critical solution temperature (UCST) behaviour was observed. For x 0.8-0.9, maximum critical temperature was found. As molecular weight of P4VP was increased, phase transition occurred at higher temperature. It was found that phase behaviour of the bottle-brush was affected by mobility of P4VP as well as size and regularity of lamellar structure. The $L_{p}$ determined from analysis of crystal structure was in the range of 35 $\AA$ and 40 $\AA$ and was more affected by the molecular weight of P4VP than by mole ratio (x). However, if the molecular weight of P4VP was high, LP value was little affected.ted.d.

  • PDF