Lecture 6 Hybrid POSS

1. Lecture 6 Hybrid POSS Class 1B: inorganic phase is made in-situ in organic continuous phase. in situ means “in place”

2. 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.

3. Preparation by dissolving inorganic monomer in solid organic polymer then polymerizing to form particles Solid Organic Polymer Inorganic Monomer (liquid) & catalyst •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

4. 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

5. 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

6. Polymers used in class 1B systems • Elastomers: silicone, polybutadiene, polyisoprene • Thermoplastics: polyurethanes, polycarbonates, polyvinylalcohol, polyacrylates, polysulfones, polyethylene oxide (PEO), polypropylene oxide (PPO) • Thermosets: epoxies • Polyionomers: Nafion

7. 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

8. 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

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

10. 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

11. Hydrolysis & condensation of RSi(OR)3

12. 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

13. 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

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

15. 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

16. Reduction of metals

17. Metal and Semiconducting Sulfides

18. Class 1B: 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

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

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

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

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

23. Silver particles made in situ polydimethylsiloxanes

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

25. Class 1B: 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.