Control of calcium carbonate crystallization by using anionic polymethylsiloxanes as templates Andro ´ nico Neira-Carrillo a,n , Patricio Va ´ squez-Quitral a , Marı ´a Paz Dı ´az a , Marı ´a Soledad Ferna ´ ndez a , Jose ´ Luis Arias a , Mehrdad Yazdani-Pedram b a Faculty of Veterinary and Animal Sciences, University of Chile, Santa Rosa 11735, PO Box 2-15, Santiago, Chile b Faculty of Chemical and Pharmaceutical Science, University of Chile, S. Livingstone 1007, PO Box 233, Santiago, Chile article info Article history: Received 5 March 2012 Received in revised form 23 May 2012 Accepted 27 May 2012 Available online 13 June 2012 Keywords: Polymethylsiloxane Hydrosilylation Gas diffusion method Calcium carbonate abstract Sulfonated (SO 3 H-PMS) and carboxylated (CO 2 H-PMS) polymethylsiloxanes were synthesized and their effects as anionic template modifier on the CaCO 3 crystal morphologies were evaluated. In vitro crystallization assays of CaCO 3 were performed at room temperature by using gas diffusion method at different concentration, pH and time. SEM images of CaCO 3 showed well-defined short calcite piles (ca. 5 mm) and elongated calcite (ca. 20 mm) when SO 3 H-PMS was used. When CO 2 H-PMS was used, the morphology of CaCO 3 crystals was single-truncated at pH 7–9 and aggregated-modified calcite at pH 10–11. However, at pH 12 the least stable donut-shaped vaterite crystals were formed. EDS and XRD confirmed the presence of Si from anionic PMS templates on the CaCO 3 surfaces and its polymorphism, respectively. Results showed that the selective morphologies of CaCO 3 reflect the electrostatic interaction of anionic groups of functionalized PMS with Ca 2 þ adsorbed on CaCO 3 crystals. Rounded and truncated-modified fluorescent CaCO 3 was also produced by the inclusion of functionalized PMS into the lattice of CaCO 3 matrix. We demonstrated that the anionic PMS offer a good modifier for polymer-controlled crystallization and a convenient approach for understanding the biomineralization field. & 2012 Elsevier Inc. All rights reserved. 1. Introduction Biomineralization is the process by which living organisms produce biological composites and exert precise control over minerals they deposit, creating bioceramic materials with uni- form particle sizes, novel morphologies, myriad shapes and sizes that are often of high strength and remarkable properties [1,2]. This process offers an organism more than just structural support and mechanical strength. As nature  s master builder, it is involved in a wide variety of important biological functions such as: protection, motion, cutting and grinding, buoyancy, storage, optical detection, magnetic and gravity sensing. Examples of bioceramic are mollusk and egg-shells, crustacean carapaces, bones, teeth, etc. Therefore, molecular processes involved in this process are of great interest to materials scientists whom seek to manufacture bio-composites and analogous hybrid materials to those formed in nature. Abundant efforts in search of innovative biomimetic processing strategies to produce e.g., inorganic thin films has been performed [3,4]. The majority of these efforts have focused on exploring the promoting or inhibiting effects of polymeric additives as templates on crystal nucleation and growth [5]. Several approaches can be discerned, according to the nature and structural complexities of the templates employed and have been performed on the in vitro [6–9] or in vivo [10–12] assays. Templates used in in vitro refer to those substrates with particular sequence fragments that could mediate special mineral crystals. The presence of biomacromolecules turns the deposition process of calcium carbonate (CaCO 3 ) from homogeneous nuclea- tion to heterogeneous nucleation, and the reaction condition reaches the kinetic limitation requirements. Thus, polymer mole- cules adsorbed on the glass substrate can provide the conditions for heterogeneous nucleation of aragonite crystals, which is then under certain condition energetically more favorable than homo- geneous nucleation of calcite crystals in solution. These investiga- tions have yielded valuable information on how organic matrix can affect biomineral formation [3–5,7]. CaCO 3 is one of the most studied inorganic material, which has facilitated the understanding of biological control of biominer- alization [13,14]. It has found abundant applications in the paper, textile, paint, rubber and adhesive industries. It is well known that anhydrous CaCO 3 have three polymorphs: rhombohedric calcite, orthorhombic aragonite and hexagonal vaterite with decreasing stabilities and increasing solubility limits in aqueous environment at 25 1C. Their solubility constant (Ksp) values are Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/jssc Journal of Solid State Chemistry 0022-4596/$ - see front matter & 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jssc.2012.05.039 n Corresponding author. Fax: þ56 2 9785526. E-mail address: aneira@uchile.cl (A. Neira-Carrillo). Journal of Solid State Chemistry 194 (2012) 400–408