20882-04-6Relevant articles and documents
Synthesis and self-assembly of stimuli-responsive amphiphilic block copolymers based on polyhedral oligomeric silsesquioxane
Hong, Lizhi,Zhang, Zhenghe,Zhang, Yuan,Zhang, Weian
, p. 2669 - 2683 (2014)
A novel POSS-containing methacrylate monomer (HEMAPOSS) was fabricated by extending the side chain between polyhedral oligomeric silsesquioxane (POSS) unit and methacrylate group, which can efficiently decrease the steric hindrance in free-radical polymerization of POSS-methacrylate monomer. POSS-containing homopolymers (PHEMAPOSS) with a higher degree of polymerization (DP) can be prepared using HEMAPOSS monomer via reversible addition-fragmentation chain transfer (RAFT) polymerization. PHEMAPOSS was further used as the macro-RAFT agent to construct a series of amphiphilic POSS-containing poly(N, N-dimethylaminoethyl methacrylate) diblock copolymers, PHEMAPOSS-b-PDMAEMA. PHEMAPOSS-b-PDMAEMA block copolymers can self-assemble into a plethora of morphologies ranging from irregular assembled aggregates to core-shell spheres and further from complex spheres (pearl-necklace-liked structure) to large compound vesicles. The thermo- and pH-responsive behaviors of the micelles were also investigated by dynamic laser scattering, UV spectroscopy, SEM, and TEM. The results reveal the reversible transition of the assembled morphologies from spherical micelles to complex micelles was realized through acid-base control. 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2669-2683 Stimuli-responsive amphiphilic diblock copolymers of PHEMPOSS-b-PDMAEMA with a high degree of polymerization of the POSS unit were synthesized via RAFT polymerization. The self-assembled morphologies of PHEMAPOSS-b-PDMAEMA in aqueous solution can be tuned from irregularly assembled aggregates into spherical core-shell micelle and from pearl-necklace-liked structure into large compound vesicles by varying the length of hydrophilic PDMAEMA block chain. Copyright
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.
