Synthesis of Polyisobutylene-Silica Hybrid Stars and Networks. via Sol-Gel Processing

Transcription

1 Synthesis of Polyisobutylene-Silica Hybrid Stars and etworks via Sol-Gel Processing Formal Seminar 4/12/00 By: Stewart Lewis

2 1 Presentation utline Research objectives The sol-gel process and basic sol-gel chemistry Brief discussion of hybrid materials Polysilsesquioxanes RMSILs (organically modified silicates) Preliminary results on polyisobutylene-silsesquioxanes stars Conclusions Acknowledgements

3 2 Research objectives: Adaptation of sol-gel processes for facile/efficient synthesis of PIB with inorganic moieties for the production of novel hybrid stars and networks. Examination/testing of the physical properties of these novel constructs.

4 Hybrid materials: organic materials physically or chemically bound to ceramics (nonmetallic, inorganic materials). Types 10 Since 1975 Since 1985 Since 1995 Ceramic-polymer (CERAMER) nanocomposites Polymer layered silicate nanocomposites Polyhedral oligomeric silsesquioxane (PSS) nanocomposites

5 11 Hybrid materials offer the high strength of ceramics while providing the toughness and potential for processibility inherent of organic polymers. Potential applications Reinforced polymers Toughened ceramics Protective coatings ptical devices Adhesives

6 3 Sol-gel techniques are instrumental for the synthesis of hybrid materials. Ceramics are usually formed at high temperatures that degrade organic materials. The sol-gel process offers low temperature routes for syntheses. Sol-gel chemistry provides a means for chemically bonding organic materials to ceramics.

7 4 The term sol-gel refers to changes that occur as metalorganic monomers are polymerized to ceramics. Visualization of the sol-gel process Monomer Dimer Cyclics Particles ph < 7 no salts ph 7-10 with salts 1 nm ph 7-10 no salts 10 nm 100 nm Three-dimensional networks (gels) Sols

8 5 Typical metalorganic monomers Si Si tetramethoxysilane (TMS) tetraethoxysilane (TES) Bu Bu Ti Bu Si Si Bu titanium n-butoxide (TB) hexamethoxydisiloxane readily available easily purified react readily with water to form chemically pure ceramics.

9 6 Sol-gel chemistry primer Acid or base catalyzed reactions Hydrolysis of metal alkoxides hydrolysis Si R + H 2 Si H + RH esterification Condensation condensation Si R + H Si Si Si + RH alcoholysis Condensation condensation Si H + H Si Si Si + hydrolysis H 2 Condensation may commence before hydrolysis is complete.

10 7 Effect [H 2 ] : [Si(R) 4 ] = r, on the kinetics of gelation 3 hours r = 4 r = days 29 Si MR spectra of acid-catalyzed TES (r = 2). Chemical shift, (ppm), relative to TMS. 1 Disappearance of unhydrolyzed TES during acid-catalyzed hydrolysis ( 29 Si MR) R. A. Assink, unpublished. 2. J.C.Pouxviel, J.P. Boilet, J.C. Beloeil, and J.Y. Lallemand, J. on-crystalline Solids, 89 (1987) 345.

11 8 Effect of catalyst strength/concentration on gelation kinetics ph rate profile for the hydrolysis of phenyl tris(2-methoxyethoxy)silane in aqueous solution. 3 Gel time versus ph of reacting sols prepared from TES (r = 4) Pohl, E.R.; sterholtz, F.D. Molecular Characterization of Composite Interfaces; Plenum: ew York, 1985; p Coltrain, B.K.; Melpolder, S.M.; Salva, J.M. Proceedings of the IVth Int l. Conference on Ultrastructure Processing of Ceramics, Glasses, and Composites; Tucson, AZ, Feb., 19-24, 1989, p 125.

12 9 Effect of alkoxide and alkyl substituent structure on gelation kinetics Rate Constants for Acid Hydrolysis of Alkoxyethoxysilanes (R) n Si(Et) 4-n at 20 C. 5 ( ) 5 CH R n k, 10 2 (l mol. -1 s -1 [H + ] -1 ) C CH CH Acid catalyzed hydrolysis/condensation of methoxysilane monomers. 6 tr. bl. = translucent blue, trp. = transparent, op. = opaque, prcp. = precipitate, vsc. = viscous, crst. = crystals Polymerization Results Monomer Acid-Catalyzed Base-Catalyzed Water Si(Me) 4 tr.bl. gel trp. gel tr.bl. gel MeSi(Me) 3 gel tr.bl. gel vsc. oil EtSi(Me) 3 resin resin/crst. resin t-busi(me) 3 prcp. crst. prcp. C 5. Aelion, R.; Loebel, A.; Eirich, F. J. Am. Chem. Soc., 1950, 72, Loy, D.A.; Baugher, B.M.; Schneider, D.A. J. Polym. Prepr., Am. Chem. Soc., Div. Polym. Chem., 1998, 39(2), 418.

13 12 Formation of polysilsesquioxanes n RSi(R') 3 + 3/2n H 2 H or H [RSi 3 / 2 ] n + 3n R'H Structures of polysilsesquioxanes Si R n = even integer Polyhedral oligomeric silsesquioxanes (PSS). R = H,, allyl, etc. n = infinity Amorphous networks.

14 13 PSS copolymers 7 X 2 SiR 2-2 HX X = Cl, Me 2 Exodisilanol R, comonomer T g ( C) T m ( C) T dec ( C) M n x10-3 a M w x10-3 a a M w /M n DP Me Me, Vinyl Me, Me(SiMe 2 ) 2 SiMe a From GPC measurements. 7. Lichtenhan, J.D.; go, Q.V.; Carter, J.A.; Gilman, J.W.; Feher, F.J. Macromolecules 1993, 26(8),

15 14 PSS macromonomers 8 methacryloyl-simecl 2 Et 3 /CHCl 3 25 C Et 4 H PSS-methacrylate THF/H 2 Endodisilanol R = i-bu, vinyl, c-c 5 H 9, c-c 6 H 11 norbornyl-simecl 2 Et 3 /CHCl 3 25 C PSS-norbornyl 8. Feher, F.J.; Terroba, R.; Ren-Zhi, J.; Wyndham, K. D.; Lucke, S.; Brutchey, R.; guyen, F. Polymeric Materials: Science and Engineering 2000, 82, 235.

16 Sol-gel synthesis of polystyrene stars 9 1. Precursor synthesis CH CH + x H C Li M n M n 15 ( H MR) ( H MR) (GPC) (GPC) 1 a M n M w /M n a Ratio repeat unit resonance to initiator fragment b Ratio repeat unit resonance to Si(R) 3 Cl Si( ) 3 THF, -78 o C H Si( ) 3 CH CH C x THF 1.0 M HCl 29 Si MR of triethoxysilyl terminated PS. 9. Long, T.E.; Kelts, L.W.; Mourey, T.H.; Wesson, J.A. In Star and Hyperbranched Polymers; Mishra, M.K.; Kobayashi, S., Eds.; Marcel Dekker: ew York, 1999; pp

17 16 Sol-gel synthesis of polystyrene stars 2. Linking of precursors to stars H Si(H) 3 CH CH x C - H H Effect of precursor M n on star growth at 120 C/240 hours. Precursor M n Condensate M p umber of arms 2,100 35, ,400 84, , , CH CH x H Si H H Si H CH CH CH x + precursor arm - H 2 CH CH x H Si H H H Si Si H CH CH CH x CH CH CH x

18 17 RMSILs: Polyoxazoline-silica hybrids 10 Ts n Ts H 2 Si(Et) 3 n+1 H 2 Si(Et) 3 Ts Ion Exchange Resin n+1 H Si(Et) 3 Ts Ts Ts Ts n m Ts 1) H 2 Si(Et) 3 2) Ion Exchange Resin (Et) 3 Si H n+1 H Si(Et) m+1 3 Initiator Time (h) Yield (%) M n ( 1 H MR) MeTs Bifunctional Saegusa, T.; Chujo, Y;, Ihara, E.; Kure, S. Macromolecules 1993, 25,

19 18 PZ DP a PZ/Si(Et) 4 (g/g ) PZ (wt %) b H 2 content c (Et) 3 Si 9.0 1/ (Et) 3 Si / (Et) 3 Si 9.0 1/ (Et) 3 Si Si(Et) / Silica gel 1.53 a Calculated from the feed ratio b Calculated from elemental analysis c (grams wet gel)/(grams dried gel) Schematic representation of polyoxazoline-modified silica gel. Illustration of the interaction between a polyoxazoline segment and the silica matrix of a hybrid material.

20 Response (mv) 19 Sol-gel synthesis of PIB silsesquioxane stars 1. Synthesis of allyl terminated PIB C Cl + n C + TiCl 4 Typical SEC data for allyl terminated PIB a M n M w M w /M n 9,400 10, a relative to narrow polyisobutylene standards C 6 H 14 / Cl (60/40, vol/vol) DMA DtBP -80 o C C C C Cl n-1 1) CH Si 2) MeH C C n CH Time (min)

21 20

22 Response (mv) 21 Sol-gel synthesis of PIB silsesquioxane stars 2. Synthesis of triethoxysilyl terminated PIB Typical SEC data for triethoxysilyl terminated PIB a M n M w M w /M n 9,300 10, a relative to narrow polyisobutylene standards C C CH n Et + H Si Et Et THF/ 70 o C/ Ar(g) Pt catalyst Et C C Si Et n Et THF/70 o C 1.0M HCl Time (min) Typical 1 H MR results for hydrosilylation of allyl terminated PIB with triethoxysilane

23 Response (mv) 22 Sol-gel synthesis of PIB silsesquioxane stars 3. Linking of precursors to stars H C C Si H n H + 3 EtH - H 2 R C C Si n R R R = H Si C H C n or H Time (min) Typical SEC data for acid catalyzed condensation of triethoxysilyl terminated PIB a M n M w M w /M n umber of arms % b Precursor 9,300 10, Condensate 32,800 35, a relative to narrow polyisobutylene standards b determined by comparison of peak areas

24 Response (mv) 23 Sol-gel synthesis of PIB silsesquioxane stars 4. Synthesis and linking of trichlorosilyl terminated PIB C C CH n Cl + H Si Cl Cl THF/ 70 o C/ Ar(g) Pt catalyst Cl C C Si n Cl Cl THF/H 2 70 o C H C C Si H + 3 HCl n H - H 2 R C C Si R n R R R = Si C C or H n R Time (min) SEC data for uncatalyzed condensation of trichlorosilyl terminated PIB a M p M n M w M w /M n % b Precursor 9,600 9,300 10, Condensate 455, , , a relative to narrow polyisobutylene standards b determined by comparison of peak areas

25 24 Conclusions ver the past several decades, interest in hybrid materials has grown. This developing area requires attention. PIB can be functionalized with groups that can participate in sol-gel processes. This provides a link between sol-gel chemistry and living carbocationic polymerization. The combination of these two techniques will give rise to novel materials which may possess improved/useful properties.

26 25 Acknowledgements SF Dr. Kennedy My group members, especially Dr. Pi and Pious Kurian