碳酸钙在聚合物胶束控制下的仿生合成

合成了温敏性的聚(N-异丙基丙烯酰胺)-b-聚(L-谷氨酸)(PNIPAM-b-PLGA)嵌段共聚物,在较高温度下制备了以PNIPAM为核、以PLGA为壳的自组装胶束,研究了胶束对碳酸钙晶体生长的控制作用.使用扫描电镜和X射线衍射表征了碳酸钙晶体的形貌和晶型.当聚合物胶束浓度较高时,得到纤维状的文石;当胶束浓度较低时,...

BIOMIMETIC SYNTHESIS OF CALCIUM CARBONATE UNDER CONTROL OF POLYMERIC MICELLES

Poly(N-isopropylacrylamide)-b-poly(L-glutamic acid)(PNIPAM-b-PLGA) block copolymers were synthesised,and polymeric micelles were prepared at high temperatures.The polymeric micelles were employed to control the crystallization of calcium carbonate(CaCO3) by the gas diffusion method.Scanning electron microscopy and X-ray powder diffraction were used to study the CaCO3 morphologies and polymorphs.When the concentration of micelles is high,nest-like super-structures with diameters about 50 μm were observed.The super-structures composed of aragonite fibres with large ratios of length to diameter.And droplet-like growth points were frequently found at the end of fibres.While a lower concentration of micelles led to the formation of irregular vaterite particles.From the time-resolved experiments,the mechanism of crystals formation was proposed.First,polymer-induced liquid-precursor(PILP) amorphous CaCO3 was induced by the micelles,and then the precursors grew into one-dimensional fibres through an attaching-solidifying process.For the strong interaction between copolymers and calcium ions,a higher concentration of micelles could retard crystallization of the precursors and induce the formation of aragonite fibers.While lower concentration of micelles made the crystallization less inhibited,and thus led to the formation of vaterite particles.Control experiments showed that such PILP process could not be induced by PNIPAM,PLGA homopolymers and PNIPAM-b-PLGA block copolymers dilute solution(25℃,no well defined aggregates were formed).Therefore,PNIPAM-b-PLGA micelles play a crucial role in the formation of CaCO3 liquid-like precursor precursors and aragonite fibre growth.The present investigation of the influence of PNIPAM-b-PLGA micelles on CaCO3 crystallization is helpful for the understanding of the PILP process and fabricating other fibrous inorganic materials.