화학공학소재연구정보센터
Langmuir, Vol.25, No.16, 9525-9534, 2009
Internally Self-Assembled Thermoreversible Gelling Emulsions: ISAsomes in Methylcellulose, kappa-Carrageenan, and Mixed Hydrogels
Self-assembled thermo-gelling emulsions were developed by blending internally self-assembled particles (ISAsomes) with thermoreversible polysaccharide hydrogels of methylcellulose (MC), kappa-carrageenan (KC), and their 1:1 mixture. In this way, the hierarchical structure of ISAsome samples wits successfully promoted. The gelified polymer network corresponds to the highest level of the hierarchical structure and as such represents the capturing matrix for the medium structural level, i.e., dispersed emulsion particles. which are further internally structured its the lowest level of structure. Utilizing small-angle X-ray scattering, differential scanning calorimetry, dynamic light scattering, and oscillatory rheological experiments in the temperature regime from 20 to 70 degrees C, we were able to show that the ISAsomes stay practically intact during such embedment into a hydrogel matrix retaining its internal self-assembled Structure and its functionality. The characteristic sot-gel and gel-sol transition temperatures of the ISAsome-loaded hydrogel samples showed a slight shift in comparison to the unloaded hydrogel samples. Furthermore, we found that MC is actually able to stabilize the ISAsomes at higher temperatures (tests were conducted up to 90 degrees C). Gels made from MC and KC show quite different features in terms of rheology and differential scanning calorimetry, However, the most interesting results were obtained for the ISAsome-loaded MC-KC (1:1) gelifying system, which behaves as it low- and high-temperature gel with a narrow intermediate temperature window where it is a sot. This specific thermal behavior allows for easy temperature tuning of the system's aggregate state as well its the internal self-assembled structure. As such, this system is suggested to be further tested as the potential media for it temperature-controlled burst/sustained release media of various hydrophilic, hydrophobic, or amphiphilic guest functional molecules.