Polymer(Korea), Vol.33, No.5, 501-508, September, 2009
광산란과 점성도법에 의한 폴리감마글루탐산 나트륨 염의 열분해 분석
Analysis on Thermal Degradation of Poly(γ-glutamic acid) Sodium Salt by means of Light Scattering and Viscometry
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초록
폴리감마글루탐산의 나트륨 염(sodium salt of poly(γ-glutamic acid))의 고체상과 용액상에서의 열분해 실험을 57∼120 ℃ 부근에서 실시하였고, 점성도법과 광산란법을 이용하여 분자량 감소 결과를 시간의 함수로 분석하였다. 고체상에서의 분해 결과는 사슬 절단 속도가 시간에 무관하게 일정하며, 사슬 내에서의 절단 위치 또한 무작위하다는 것을 보여주었다. 특히, 용액상에서의 시간에 따른 분해과정은 특성분해시간 t*로 스케일링된 환산시간 t/t*를 이용하여 분자량 또는 고유점성도를 도시할 경우 서로 다른 온도에서의 분해 과정은 하나의 표준곡선 위에 놓임을 알 수 있었다. 특히, 용액상에서의 분해곡선은 지수함수와 선형식의 합으로 표시할 수 있었으며 지수함수는 분해 초기에 뚜렷이 나타났다. 또한, 고체상 분해와 용액상 분해 모두 활성화 에너지는 107∼115 kJ/mol로써 측정되었으며 문헌치와 좋은 일치를 보여준다.
The thermal degradation experiment of sodium salt of poly(γ-glutamic acid)(PGGNa) has been
carried out in both its solid phase and solution phase at the range of 57∼120 ℃ and their molecular weight decreasing effect was analyzed as a function of time by means of viscometry and light scattering. Based on the solid phase degradation results, it was supposed that the bond scission rate in a polymer chain kept constant and that the bond scission was occurred on a randomly located position in a polymer chain. For the degradation in solution phase, it was also found that all data at various temperatures were dropped on a single master curve when the reduced time t/t* was used in the plot of the reciprocal intrinsic viscosity (or molecular weight). This degradation curve in solution phase could be expressed as the sum of a single exponential and a linear equation and especially, the single exponential character appeared only at the beginning stage. The activation energy was measured as 107∼115 kJ/mol in this study and agreed with the literature values.
Keywords:thermal degradation;poly(γ-glutamic acid);characteristic degradation time;master curve;activation energy.
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