Physics and Chemistry of Hybrid Organic-Inorganic Materials Lecture 11: Polymerizing organic monomers in inorganic materials

Key concepts Reasons for making an inorganic filled organic polymer hybrid: improve strength, abrasion resistance, modulus, hardness, inflammability, Metal oxide inorganic particles can be made by sol-gel, flame synthesis Organic phase: organic polymers Inorganic particles increase viscosity Particle aggregation ruins hybrid effects smaller the particle, the greater the strength and modulus of the hybrid the higher the particle concentration, the greater the strength and modulus of the hybrid

Making Hybrid Materials: Class 1C (Polymerizing in pores) Porous metal oxide Liquid monomer (no solvent) UV, heat, radiation Non-porous composite material

Making Hybrid Materials: Class 1C (Polymerizing in pores) 1) Monolithic inorganic Polymer nanocomposite from completely filling pores 2) Reinforced xerogel or aerogel by coating aggregated particles with polymer 3) Polymerizing intercalated monomers in clay 4) Polymer surrounding colloid crystal of inorganic

First example: Monolithic inorganic Polymer nanocomposite from completely filling pores Infiltration & polymerization of monomer in pores of gel Provides a percolating filler phase based on the original gel skeleton Acc. Chem. Res., 2007, 40 (9), 810–818

First example: Monolithic inorganic Polymer nanocomposite from completely filling pores Pope, E. J.; Asami, M.; Mackenzie, J. D. Transparent silica gel–PMMA composites J. Mater. Res Transparent, tough, tailorable refractive index, abrasion resistant

Reinforced xerogel or aerogel by coating aggregated particles with polymer Porous materials, like aerogels, are super thermal insulation, but very weak Monomers, such as superglue, can be polymerized directly on surface by chemical vapor deposition Boday, D. J.; Stover,. J.; Muriithi, B.; Keller, M. W.; Wertz, J. T.; DeFriend Obrey, K. A.; Loy, D. A. ACS Applied Materials & Interfaces 2009, 1(7), 1364.

Reinforced xerogel or aerogel by coating aggregated particles with polymer Epoxies, urethanes, some vinyl polymers monomers can be polymerized in solution if they will precipitate onto the particles surfaces. Acc. Chem. Res., 2007, 40 (9), pp 874–884

Polymer-Clay Nanocomposites from intercalation & polymerization of monomers A. Usuki, Y. Kojima, M. Kawasumi, A. Okada, Y. Fukushima,T. Kurauchi, O. Kamigaito, "Synthesis of nylon 6-clay hybrid," J. Mater. Res. 1993, 8, ) First heat 100 g montmorillonite (MMT) with 51.6 g of aminolauric acid and 24 mL conc. HCl in 10 Liters of water for 10 min. 2) Filter, was 3X with 10 L hot water, then freeze dry, then dry under vacuum at 100 °C to afford ion exchanged, intercalated MMT 3) Mix 29.7 g intercalated MMT, 509 g caprolactam, and 66 g 6- aminocaproic acid were mixed in mortar in pestle. 4) The mixture was polymerized in3000 mL round bottom flask with mech. Stirrer and under nitrogen for 30 min at 100 °C then for 6 h at 250 °C. 5) The products were crushed in mortar & pestle, then washed with water and dried at 89 °C.

Polymer colloidal crystal nanocomposites Microporous and Mesoporous Materials 2001,44-45, ) Prepare a colloidal crystal (opal) from silica particles 2) Add monomer & catalyst to fill pores 3) Polymerize to form72% by volume silica filled organic polymer 4) Dissolve silica away with HF if inverse opal is desired

Small organic phase dispersed in continuous inorganic phase

Making Hybrid Materials: Class 1D (encapsulation of small organics) Polymerize metal oxide around organic pores must be small or leakage will occur Solid state dye lasers, filters, colored glass sunscreens Biopolymers Medicines Living cells Imprinting (artificial enzymes)

Class 1D: the organic dye is trapped within the silica network

Simple method for encapsulating dyes.

Easily recyclable colored bottles J. Livage

Organic dyes in a silica matrix fluorescence - laser - NLO - photochromism J. Livage

nonlinear hybrid C 60 -silica coated lenses Optical limiters

Absorption spectrum of the UV protecting film (1 µm) with and without the UV-absorber molecule (34 wt%). Chem. Soc. Rev., 2007, 36, Preventing UV-light damage of light sensitive materials using a highly protective UV-absorbing Hybrid (Class 1D) coating

Visible absorption spectra of Photosystem I entrapped in sol–gel at intervals during the aging process compared with the solution spectrum of the native preparation. The spectrum of a control gel without PSI that was aged for 29 days is also shown H. O'Neill and E. Greenbaum, Chem. Mater., 2005, 17, 2654 Dyes are protected against photodegradation by Class 1D matrix

Fluorescent core–shell silica nanoparticles incorporating organic dyes with different spectral characteristics, covering the entire UV-vis absorption and emission wavelengths. (Reproduced from ref. 31, with permission. Copyright 2005 American Chemical Society.)ref. 31 H. Ow, D. R. Larson, M. Srivastava, B. A. Baird, W. W. Webb and U. Wiesner, Nano Lett., 2005, 5, 113

Sol-gel encapsulation of drugs in silica particles using microemulsions Water in oil emulsions Langmuir, 1997, 13 (24), pp 6400–6406

Chem. Soc. Rev., 2007, 36, Enzymes in sol-gel Requires mild sol-gel (pH 7) Enzymes remain active longer than when in water Sensors and catalysts Science 1992, 255, 1113– 1115

Cyctochrome C encapsulated in dry aerogels Generally thought that water is needed for enzyme activity Aerogels made with cytochrome C have remained active NO sensors Amanda S. Harper-LeathermanAmanda S. Harper-Leatherman Langmuir, Article ASAP 2012

Chem. Mater., 2005, 17 (10), pp 2654–2661 Bio encapsulation: Photosynthesis system

Enclapsulation of liposomes in silica gel Langmuir, 1997, 13 (19), pp 5049–5053

Bacteria encapsulated within a silica matrix aged for (a) 1 month without glycerol and (b) 1 day with a layer of glycerol.silicaglycerol Encapsulating living cells in silica

Imprinting to make synthetic enzymes in hybrid materials

Chem. Mater., 2003, 15 (19), pp 3607–3613 Imprinting dopamine analogs into silsesquioxane modified silicas for sensors

Imprinting DDT into silsesquioxane modified silicas for sensors

C. Lin, A. Joseph, C.K. Chang, Y.C. Wang, Y.D. Lee Anal. Chim. Acta, 481 (2003), p. 175 Imprinting Caffeine into silica modified with silsesquioxane with non-bonding interactions

C.W. Hsu, M.C. Yang, J. Non-Cryst Solid, 354 (2008), p Imprinting dopamine analogs into silsesquioxane modified silicas for sensors

Acc. Chem. Res., 2007, 40 (9), pp 756– 767 Imprinting that generates on optical signal when site recognizes molecule

Summary Inorganic surfaces are best modified using silane coupling agents (hydrolyzed organotrialkoxysilanes or oligosilsesquioxanes). Organic monomers can be added as liquid to a porous inorganic material or adsorbed as a gas before polymerizing in the pores. The resulting hybrids are stronger than the polymer alone. Organic molecules, such as dyes, can be encapsulated into inorganic materials, by polymerizing the inorganic around them. Dyes encapsulated in inorganic matrices are more stable chemically and are less potentially hazardous. enzymes and even bacteria can be encapsulated in inorganic materials Similarly, inorganic materials can be imprinted by polymering inorganic materials around a template, then removing the template to make functionalized, enzyme like pores Emulsion polymerization can be used to encapsulate organic molecules, such as sunscreens, into inorganic particles.