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Key concepts

Physics and Chemistry of Hybrid Organic-Inorganic Materials Lecture 12: Polymerizing inorganic monomers dissolved in organic polymers. Key concepts. Reasons for making an inorganic filled organic polymer hybrid: improve strength, abrasion resistance, modulus, hardness, inflammability,

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Key concepts

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  1. Physics and Chemistry of Hybrid Organic-Inorganic MaterialsLecture 12: Polymerizing inorganic monomers dissolved in organic polymers

  2. 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

  3. Making Hybrid Materials: Class 1B (in situ particle growth) Ideally, no Solvent except for monomer(s) No solvent with low tg organic polymers or in polymer melts (< 100 °C) or if monomer will is soluble in polymer. Otherwise solvent may be used to mix before casting.

  4. Preparation by dissolving inorganic monomer in solid organic polymer then polymerizing to form particles Inorganic Monomer (liquid) & catalyst Solid Organic Polymer •Polymerization by: 1) hydrolysis & condensation of M(OR)n Water diffuses into membrane from air 2) Reduction of metal compound. H2 or polymer itself as reducing agent 3) sulfidation of cations (H2S) 4) photochemical or thermal decomposition Monomer must be soluble in polymer Organic Polymer Inorganic Monomer Monomer polymerizes & forms particles

  5. Preparation by mixing inorganic monomer with liquid organic polymer & hydrolysis & condensation Liquid Organic Polymer Inorganic Monomer (liquid) & catalyst Physical mixing Very few liquid polymers, save some elastomers like polydimethylsiloxane and low molecular weight polybutadiene or polyisoprene Organic Polymer Inorganic Monomer 1) Water diffuses in from outside 2) Monomer polymerizes 3) Particles phase separate Silica-PMS materials are looked at later in lecture

  6. Preparation by mixing inorganic monomer with solid organic polymer and allowing particles to form Solid Organic Polymer Organic Polymer in solvent Inorganic Monomer (liquid) Dissolve Physical mixing Solvent must be removed before polymerization Water for hydrolysis and condensation would be diffused into dry film from air. Organic Polymer Inorganic Monomer in solvent Evaporate solvent Organic Polymer Inorganic Monomer Monomer polymerizes & forms particles Silica-Nafion materialsmade this way are looked at later in lecture Spherical particles

  7. Polymers used • Elastomers: silicone, polybutadiene, polyisoprene • Thermoplastics: polyurethanes, polycarbonates, polyvinylalcohol, polyacrylates, polysulfones, polyethylene oxide (PEO), polypropylene oxide (PPO) • Thermosets: epoxies • Polyionomers: Nafion

  8. Review of polymerizations 1) hydrolysis & condensation of M(OR)nor RSi(OR’)3 2) Reduction of metal compound 3) sulfidation of cations 4) photochemical or thermal decomposition

  9. Hydrolysis & condensation of M(OR)n: the monomers Silicon: Si(OR)4 or R’Si(OR)3 Aluminum: Al(OR)3 or AlCl3 6H2O Transition metals: Mz(OR)n or MzCln hH2O z = oxidation number for metal n = number of alkoxide or halide in monomer h = number of coordinating waters

  10. Hydrolysis & condensation of Si(OR)4 Catalyzed by acids (HCl,HNO3) or bases (NH3 aq, NaOH) or fluoride.

  11. Particles from hydrolysis & condensation of Si(OR)4 • Typically leads to amorphous spherical particles (not quartz) • Can template particles with ordered mesopores with surfactants • Stober synthesis from TEOS with NH3 and water gives monodisperse particles • Emulsion polymerization (water in oil) gives monodisperse particles • Other preps give polydisperse particles

  12. Hydrolysis & condensation of RSi(OR)3

  13. Particles from hydrolysis & condensation of RSi(OR)3 • Typically leads to amorphous spherical particles • Not as easy to prepare particles as with silica • Can template particles with ordered mesopores with surfactants • Stober synthesis from TEOS with NH3 and water affords polydisperse particles • Emulsion polymerization (two step) gives monodisperse particles

  14. Hydrolysis & Condensation of Mz(OR)n to form MOn/2 M = Al, B, Ti, Zr, Cr, Fe….. Hydrolysis: formation of monomeric MOH species Condensation: formation of “oxo” (neutral) M-O-M higher charge & higher pH More reactive, but too high shuts down condensation

  15. Hydrolysis & Condensation of Mz(OR)n to form MOn/2 Olation: formation of “oxo” (neutral) M-O-M olation >> oxolation

  16. Particles from hydrolysis & condensation of M(OR)n • Particles may be amorphous or crystalline • Some amorphous particles will crystallize with time. • Stober synthesis from TEOS with NH3 and water does not work • Emulsion polymerization (water in oil) gives monodisperse particles • Many more molecular clusters are available through olation chemistry

  17. Reduction of metals

  18. Metal and Semiconducting Sulfides

  19. in situ Silica-Nafion Nanocomposite Solid Nafion Nafion in Ethanol Si(OEt)4 (liquid) Dissolve Physical mixing Nafion & TEOS in ethanol Evaporate solvent Nafion & TEOS NafionTM Silica particles form in membrane Spherical particles

  20. in situ Silica-Nafion Nanocomposite Class 1A Class 1B 5 weight percent ex situ silica in Nafion In situ Silica particles

  21. In situ filled Silica in polydimethylsiloxanes Solid Organic Polymer Inorganic Monomer (liquid) & catalyst Organic Polymer Inorganic Monomer Spherical particles Journal of Polymer Science Part B: Polymer Physics, 2003, 41, 16

  22. In situ filled Silica in polydimethylsiloxanes •Highly transparent •Does not require mechanical blending Journal of Polymer Science Part B: Polymer Physics, 2003, 41, 16

  23. In situ filled Silica in polydimethylsiloxanes Journal of Polymer Science Part B: Polymer Physics, 2003, 41, 16

  24. Silver particles made in situ polydimethylsiloxanes

  25. Templating with triblock copolymer is formally a Class 1B material Polymer is template. After removal, silica remains

  26. Summary: In situ formation of inorganic phases in polymers • Method for mixing at nanoscale without mechanical blending required-less chance for aggregation and segregation to occur (steric stabilization) • Raises modulus and strength of materials • In situ polymerization of inorganics selectively in blocks of block copolymers-first step to biomimetic mineralization.

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