Synthesis of Size-Controlled Acid-Resistant Hybrid Calcium Carbonate Microparticles as Templates for Fabricating "Micelles-Enhanced" Polyelectrolyte Capsules by the LBL Technique

• Published in: Chemistry : a European journal Vol. 12; no. 22; pp. 5770 - 5778
• Main Authors: Li, Xiaodong, Hu, Qiaoling, Yue, Linhai, Shen, Jiacong
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 24.07.2006; WILEY‐VCH Verlag
• Subjects: acid resistance; Acids - chemistry; Acrylates - chemistry; block copolymers; Calcium Carbonate - chemistry; Capsules - chemical synthesis; crystal growth; Electrolytes - chemistry; layer-by-layer technique; Micelles; Microscopy, Electron, Scanning; Microspheres; Particle Size; Polystyrenes - chemistry
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200600349

Size‐controlled, low‐dispersed calcium carbonate microparticles were synthesized in the presence of the amphiphilic block copolymer polystyrene‐b‐poly(acrylic acid) (PS‐b‐PAA) by modulating the concentration of block copolymer in the reactive system. This type of hybrid microparticles have acid‐resistant properties. By investigating the aggregation behaviors of PS‐b‐PAA micelles by transmission electron microscopy (TEM), the mechanism of hybrid calcium carbonate formation illustrated that the block copolymer served not only as “pseudonuclei” for the growth of calcium carbonate nanocrystals, but also forms the supramicelle congeries, a spherical framework, as templates for calcium carbonate nanocrystal growth into hybrid CaCO3 particles. Moreover, this pilot study shows that the hybrid microparticle is a novel candidate as a template for fabricating multilayer polyelectrolyte capsules, in which the block copolymer is retained within the capsule interior after core removal under soft conditions. This not only facilitates the encapsulation of special materials, but also provides “micelles‐enhanced” polyelectrolyte capsules. Size‐controlled acid‐resistant hybrid CaCO3 microparticles were synthesized in the presence of block copolymer PS‐b‐PAA, which served not only as “pseudonuclei” for CaCO3 nanocrystal growth (1), but also forms supramicelle congeries (2), templates for nanocrystal growth into hybrid CaCO3 particles (3). Oppositely charged polyelectrolyte was deposited alternatively onto the template hybrid microparticles by the LBL technique (4). The templates were removed (5) to give “micelle‐enhanced” polyelectrolyte (PE) capsules (6). (PS=polystyrene; PAA=poly(acrylic acid).)