• 한국세라믹학회지
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• 제26권4호
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• pp.575-582
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• 1989

The effects of raw material feeding procedures and gelation temperatures on zeolite synthesis are investigated. Thus, the synthesis of zeolite 4A from sodium aluminate and sodium silicate solutions is chosen as a model reaction, for which equi-molar hydrogelation is performed with variation of feeding procedures and gelation temperatures. The formation of crystal nuclei, often being referred to as precursors, is induced under different conditions, the variation being examined by means of viscosity and water contents. The final products of zeolite 4A are evaluated by XRD, SEM morphology, particle size analysis and cation exchange capacity. Evidence shows that the viscosity of the initial products and their water contents are markedly influenced by the feeding methods of the reactant materials and by the gelation temperature. Further, it is found that the gelation at an elevated temperatures near 7$0^{\circ}C$ can be made possible through modification of mixing procedures. This provides convenient means of controlling the particle size of the final products. In this regard, a continuous flow-type mixing technique is proposed, which is demonstrated to be superior to the conventional batch-type mixings. The significance of this finding may lie in savings of equipment as well as energy costs, especialy on a large scale commercialization of zeolite production.

• Bulletin of the Korean Chemical Society
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• 제30권3호
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• pp.573-576
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• 2009

The reaction of $(en)Pd(NO_3)_2$ (en = ethylenediamine) with 1,4-bis(dimethyl-4-pyridylsilyl)benzene (L) affords cyclodimer, $[(en)Pd(L)]_2(NO_3)_4$, whereas the reaction of $(tmeda)Pd(NO_3)_2$ (tmeda = N,N,N’,N’-tetramethylethylenediamine) with L gives cyclotrimer, $[(tmeda)Pd(L)]_3(NO_3)_6$. Both complexes exist as catenane in water. The catenated cyclodimer is rigid whereas the catenated cyclotrimer is dynamic in water. The catenated cyclotrimers afford hydrogel containing 98.5% water below 2 ${^{\circ}C}$. The hydrogel changes to its sol around 38 ${^{\circ}C}$, and to its clear solution at 78 ${^{\circ}C}$. Such a notable difference between $[(en)Pd(L)]_2(NO_3)_4$ and $[(tmeda)Pd(L)]_3(NO_3)_6$ might be explained by their different dynamic behavior via ring size effects.

• 한국광물학회지
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• 제19권1호통권47호
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• pp.7-14
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• 2006

현대 산업사회의 큰 문제로 대두되고 있는 도시소각재를 용융시킨 용융슬래그를 출발물질로 하여 부가가치가 높은 P형 제올라이트를 "hydrogelation"법과 "clay conversion"법을 혼합한 새로운 방법에 의해 수열합성하였다. 출발물질은 용융슬래그 이외에 Si 공급원으로 시판되는 규산소다용액을, Al 공급원으로는 $Na_{2}O/Al_{2}O_{3}$의 비가 약 1.2인 알루민산소다용액을 사용하였다. $80^{\circ}C$의 반응 온도에서 P형 제올라이트의 최적합성조건은 $SiO_{2}/Al_{2}O_{3}$의 비율 $3.2{\sim}4.2,\;H_{2}O/Na_{2}O$의 비율 $70.7{\sim}80.0$, 그리고 반응시간이 15시간 이상일 때이었다. P형 제올라이트가 합성되었을 때, 크기가 일정하지 않은 용융슬래그 입자들은 용해되어 사라졌으며, 그 대신 균일한 크기의 P형 제올라이트 결정이 형성되었다. 암모니움 아세테이트법에 의해 측정된 합성 제올라이트의 양이온 교환능은 240cmol/kg 정도이었다.

• KSBB Journal
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• 제24권6호
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• pp.563-569
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• 2009

피브로인은 누에고치가 생산되는 불용성 단백질이다. 고온의 염화칼슘용액에서 가용화시킨 후 탈염하여 물에 녹게 만들 수 있다. 그러나 수용액은 불안정하여 피브로인 분자는 랜덤코일에서 $\beta$병풍구조의 비율이 증가하는 구조로 전이되고 겔을 형성한다. 그러나 피브로인 겔은 약하고 탄성이 없어 소재로 응용하는데 어려움이 있다. 본 연구에서는 글리세롤과 에탄올을 사용하여 반고형의 피브로인 겔을 제조하고 이들의 유동 특성을 조사하였다. 80%의 글리세롤로 만들어진 피브로인 겔은 의가소성 및 thixotropic 특성을 나타내었으며 항복응력의 제곱근 값이 피브로인의 농도와 선형적으로 비례하였으며 항복응력이 없어지는 피브로인의 농도는 0.2%로 확인되었다. 40% 에탄올에서 만들어진 피브로인 겔은 매우 심한 thixotropic 특성을 보였으며 전단속도가 어떤 값 이상이 되면 급격한 전단연화 현상을 나타내었다. 이 피브로인 겔은 전단이력 후 의가소성을 회복하는 특성을 나타내었다.

• Macromolecular Research
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• 제16권8호
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• pp.704-710
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• 2008

Injectable hydrogels are quite promising materials due to their potential to minimize invasive implantation and this provides versatile fitness irrespective of the damaged regions and facilitates the incorporation of bioactive agents or cells. In situ gel formation through stereocomplex formation is a promising candidate for injectable hydrogels. In this paper, a new series of enantiomeric, four-arm, PEG-PLA block copolymers and their stereocomplexed hydrogels were prepared by bulk ring-opening polymerization of D-lactide and L-lactide, respectively, with stannous octoate as a catalyst. The prepared polymers were characterized by $^1H$ nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared (FT IR) spectroscopy, gel permeation chromatography (GPC) and thermal gravitational analysis (TGA), confirming the tailored structure and chain lengths. The swelling and degradation behavior of the hydrogels formed from a selected copolymer series were observed in different concentrations. The degradation rate decreased with increasing polymer content in the solution. The rheological behavior indicated that the prepared hydrogel underwent in situ gelation and had favorable mechanical strength. In addition, its feasibility as an injectable scaffold was evaluated using a media dependence test for cell culture. A Tris solution was more favorable for in situ gel formation than PBS and DMEM solutions were. These results demonstrated the in situ formation of hydrogel through the construction of a stereocomplex with enantiomeric, 4-arm, PEG-PLA copolymers. Overall, enantiomeric, 4-arm, PEG-PLA copolymers are a new species of stereocomplexed hydrogels that are suitable for further research into injectable hydrogels.