1334290-05-9Relevant academic research and scientific papers
Dual stimuli-responsive poly(2-hydroxyethyl methacrylate-co-methacrylic acid) microgels based on photo-cleavable cross-linkers: PH-dependent swelling and light-induced degradation
Klinger, Daniel,Landfester, Katharina
, p. 9758 - 9772 (2011)
Dual stimuli-responsive p(HEMA-co-MAA) microgels were prepared in a facile way by inverse miniemulsion copolymerization of 2-hydroxyethyl methacrylate (HEMA) with methacrylic acid (MAA) and two kinds of newly synthesized photodegradable cross-linkers. The pH-dependent swelling behavior induced by the protonation/deprotonation of the methacrylic acid groups in the network-forming polymer was investigated by means of the particle volume change as determined by DLS measurements. Photolytic degradation experiments were conducted by irradiation with UV light which led to particle disintegration caused by cleavage of the photolabile cross-linking points. The degradation behavior of the microgels was investigated with respect to degradation rates and changes in the degree of swelling. Those parameters were found to depend on the pH value of the solvent, the light intensities, and the irradiation wavelengths applied. For similar conditions, the degradation profile was demonstrated to strongly depend not only on the molecular structure of the cross-linking molecule but also on the molecular weight of the network-forming copolymers. The particular combination of the stimuli described is designed as a new strategy to two different swelling/degradation profiles. This dual stimuli-responsiveness was shown to enable the efficient loading and subsequent release of myoglobin as a model protein. Here a slow diffusion controlled release (induced by changes of the pH) was combined with a fast degradation controlled (induced by irradiation) on-demand release. This novel two-step release profile is proposed to bear great potential for delivery applications.
Photo-sensitive PMMA microgels: Light-triggered swelling and degradation
Klinger, Daniel,Landfester, Katharina
experimental part, p. 1426 - 1440 (2012/04/23)
Two classes (type A and type B) of novel photolabile divinyl functionalized crosslinkers based on o-nitrobenzyl derivatives were synthesized and investigated with regard to their photolytic performance upon UV irradiation. The systematic variation of the molecular structure resulted in different degradation rates depending on the irradiation conditions. Thus, the successive and independent cleavage is enabled by either adjusting the applied wavelengths or irradiation times. The respective molecules were used to build up photodegradable PMMA microgels by free radical copolymerization with MMA in a miniemulsion polymerization process. UV light-induced degradation of the swollen microgels was monitored by time dependent turbidity measurements and the resulting kinetics were found to correlate with the photolysis rates of the respective crosslinkers in solution. The irradiation wavelength-controlled selective partial cleavage of type B crosslinking points was achieved by UV irradiation with λ > 315 nm and resulted in particles with extensively increased volumes consisting of highly swollen networks. In addition, the irradiation time-controlled selective complete degradation of particles containing type B crosslinkers was accomplished. By using broadband UV light containing wavelengths of λ 315 nm, the successive complete particle disintegration of type B and type A microgels was observed. Hence, the specific performance of the synthesized microgels can be precisely triggered by means of the used UV light wavelengths, doses and intensities, thus representing a great potential as new light-responsive nanoscaled materials.
