title: Intelligent core-shell nanoparticles and hollow spheres based on gelatin and PAA via template polymerization.
abstract: PAA/gelatin nanoparticles, with interpolymer complexes of gelatin and polyacrylic acid (PAA) as the cores and gelatin as the shells, were prepared via facile polymerization of AA on gelatin template. The morphology change of the nanoparticles during the reaction was traced by a combined use of dynamic light scattering (DLS) and atomic force microscopy (AFM) techniques, which revealed a discrepancy among the structure of the nanoparticles formed at different stages of the reaction: as the reaction proceeds, nanoparticles with larger compact cores and thinner shells are produced. The resultant nanoparticles are multi-responsive. Especially, they exhibit a significant temperature-dependent size change: upon raising the temperature from 25 degrees C, the nanoparticle size decreases monotonically until reaching equilibrium at about 40 degrees C. This temperature-dependence of the nanoparticle size was found to be reversible provided the nanoparticle solution was cooled at a low temperature (4 degrees C). The thermo-sensitivity of the nanoparticles is attributed to the thermo-induced sol-gel transition of the gelatin shells. In addition, the nanoparticles were further converted to hollow spheres via successive locking the shell structure by the reaction of gelatin with cross-linker glutaraldehyde, and cavitation of the cross-linked nanoparticles by switching the medium from acidic to neutral. The cavitation process was monitored by DLS, which indicated a mass decrease and size shrinkage. AFM and transmission electron microscopy (TEM) were used to trace the morphology change of the nanoparticles during the cavitation. The hollow structure was confirmed by TEM observation.
authors.affiliation: State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Material Science and Engineering, Donghua University, Shanghai 201620, PR China.
authors.forename: Yansong
authors.initials: Y
authors.lastname: Wang
authors.forename: Youwei
authors.initials: Y
authors.lastname: Zhang
authors.forename: Weiping
authors.initials: W
authors.lastname: Du
authors.forename: Chengxun
authors.initials: C
authors.lastname: Wu
authors.forename: Jiongxin
authors.initials: J
authors.lastname: Zhao
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000737:chemistry; D005780:Gelatin / Q000737:chemistry*; D005976:Glutaral / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D018625:Microscopy, Atomic Force; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D012492:Salts / Q000737:chemistry; D013696:Temperature
chemical_list: D000180:Acrylic Resins; D003432:Cross-Linking Reagents; D012492:Salts; C006903:carbopol 940; D005780:Gelatin; D005976:Glutaral