Analysis and Characterization of Monomer and Polymer Derivatives of Siloxanes

1. Analysis and Characterization of Monomer and Polymer Derivatives of Siloxanes *Ragy Ragheb, Jennifer Hoyt, Dr. J. Riffle Virginia Tech, Chemistry Dept. Summer 2002

2. Outline • Cache: comparison of monomers’ ring strain. • MW Control: • Poly(dimethyl)siloxane (PDMS) • Poly(vinylmethyl)siloxane (PVMS) • Random poly(dimethyl-co-hydridomethyl-co-cyanopropylmethyl)siloxane • Hydroxybutyl-terminated PVMS • Future Work • Acknowledgments

3. Research • Base-catalyzed ring opening polymerizations of Siloxane Monomers • Example—random poly(dimethyl-vinylmethyl)siloxane: • Base will attack the electropositive Silicon atom to open the cyclic Siloxane.

4. X = --CH3 -CH=CH2 -(CH2)3CN -(CH2)2SH n = 3 D3 D3Vi ---- ---- n = 4 D4 D4Vi D4CN D4SH Objective—CAChe Approach • Understand the affect ring size and functional groups have on ring strain. • Ring strain is calculated with a homodesmotic equation: • delta Hf values are calculated using AM1 and PM3 methods • Other properties considered: Si-O-Si and O-Si-O bond angles, Si-O bond length, and partial charge.

5. Delta Hf (kcal/mol) (AM1) Ring Strain (kcal/mol) (AM1) Detla Hf (kcal/mol) (PM3) Ring Strain (kcal/mol) (PM3) Si-O-Si bond angle O-Si-O bond angle Si-O bond length (Angs.) D3 -352 257 -393 -6.9 123 (137.1) 110 (102.9) 1.68 (1.672) D4 -483 84 -527 -10.9 164 (161.1) 104 (108.9) 1.67 (1.652) Effect of Ring Size on Ring Stain D3 D4 *Kress, J.; Leung, P.C.; Tawa, G.J.; Hay, P.J. J. Am. Chem. Soc. 1997, 119, 1954 --Conformations of both D3 and D4 were noted as planar (as seen above)

6. Introduction of Functional Groups D3Vi (3 up) D4Vi (4 up)

7. Delta Hf (kcal/mol) (AM1) Ring Strain (kcal/mol) (AM1) Si-O-Si bond angle O-Si-O bond angle Si-O bond length (Angstroms) D3 -352 257 123 110 1.68 D3Vi (3up) -282 294 142 98 1.68 D3Vi (2up) -282 294 142 98 1.68 D4 -483 84 164 104 1.67 D4Vi (4up) -391 5.8 164 104 1.67 D4Vi (3up) -391 5.5 164 104 1.67 D4Vi (2adj) -391 5.9 164 104 1.67 D4Vi (2opp) -391 5.9 164 104 1.67 Results of Vinyl Group Incorporation -Different isomers of D3Vi and D4Vi respectively were very similar -Increase in RS from D3 to D3Vi; Decrease in RS from D4 to D4Vi -Si-O-Si angle increased for the D3 to D3Vi; O-Si-O angle decreased

8. Partial Charge on Si Partial Charge on O D3 0.83 -0.56 D3Vi (3up) 0.86 -0.54 D3Vi (2up) 0.87 -0.55 D4 0.85 -0.56 D4Vi (4up) 0.89 -0.56 D4Vi (3up) 0.88 -0.56 D4Vi (2adj) 0.89 -0.56 D4Vi (2opp) 0.89 -0.56 Vinyl Group Analysis Continued -The vinyl groups introduce electron density about Si, making Si more electropositive, allowing Si-O-Si to Become more obtuse.

9. Effect of Functional Groups on Ring StrainPreliminary Points • Since isomers of the D4-X derivatives proved to have near identical properties, D4-X (4up) will only be considered in analysis. • Comparison: D4Vi vs. D4CN vs. D4SH

10. The Effect of Functional Groups on Ring Strain D4Vi D4CN D4SH

11. Delta Hf (kcal/mol) (AM1) Ring Strain (kcal/mol) (AM1) Si-O-Si Bond angle O-Si-O Bond Angle Si-O bond length (Ang) Partial Charge (Si) Partial Charge (O) D4 -483 83.7 165 104 1.67 0.845 -0.561 D4Vi -391 5.8 163 105 1.67 0.886 -0.564 D4CN -411 27.7 165 104 1.67 0.861 -0.567 D4SH -479 48.8 165 104 1.67 0.861 -0.569 The Effect of Functional Groups on Ring Strain Results -As size of functional group increases, the ring strain increases. -Close proximity of electron density to Si affects the partial charge. -Si-O bond is flexible with change in functional groups (as noted in structures).

12. Conclusions • An increase in ring size from D3 to D4 stabilizes the ring and decreases the ring strain. • The addition of larger functional groups, increases the ring strain. • Si-O-Si bond is very flexible and can withstand differences in ring strain energy. • Higher electron density about the silicon atom, causes it to be more electropositive and more prone to base attack for ring opening polymerization • CAChe proved to be reliable with AM1 but not PM3 calculations

13. Outline • Cache: comparison of monomers’ ring strain. • MW Control: • Poly(dimethyl)siloxane (PDMS) • Poly(vinylmethyl)siloxane (PVMS) • Random poly(dimethyl-co-hydridomethyl-co-cyanopropylmethyl)siloxane • Hydroxybutyl-terminated PVMS • Future Work • Acknowledgments

14. MW Control: Synthesis of PDMS and PVMS • In the synthesis of PDMS, the key difference is an assumption of 85% conversion and not 100%. For PVMS, assumption of 95% conversion and not 100%. • Possible impurities in the catalyst caused for loss of MW control.

15. PDMS 29Si NMR PDMS 29Si NMR

16. PVMS 29Si NMR

17. TGA: PVMS & PDMS --air

18. TGA: PVMS & PDMS --nitrogen

19. GPC for PDMS

20. GPC for PVMS

21. Conclusions / Future Work • Miscalculation of wt% of catalyst resulted in uncontrolled MW. • Retry synthesis with correct wt.% of catalyst. • ******WORK ON THIS SLIDE******

22. Outline • Cache: comparison of monomers’ ring strain. • MW Control: • Poly(dimethyl)siloxane (PDMS) • Poly(vinylmethyl)siloxane (PVMS) • Random poly(dimethyl-co-hydridomethyl-co-cyanopropylmethyl)siloxane • Hydroxybutyl-terminated PVMS • Future Work • Acknowledgments

23. Synthesis of Random poly(dimethyl-co-hydridomethyl)siloxane • The polymer was diluted with ethyl ether and washed with water until neutral (6 x 300mL H2O). Then rotovapped to remove excess ether. Vacuumed stripped any cyclics and H2O • Target MW: 4000 g/mol. Actual MW: 4982 g/mol (<= decrease wt.% catalyst). (x = 55.43 and y = 11.87)

24. Random poly(dimethyl-co-hydridomethyl)siloxane (1)29Si NMR

25. Synthesis of Random poly(dimethyl-co-hydridomethyl-co-cyanopropylmethyl)siloxane • Was reacted with a condenser and stirred at 130C overnight in an oil bath. There was an exotherm at 100-110 C. The Pt catalyst was a Platinum-divinyltetramethyl disiloxane complex. (225g sample) • Reaction was then heated at 150 C for 2 hours under N2, then distilled under vacuum to strip any excess allyl cyanide and toluene. • Target was to functionalize half of the hydridomethyl siloxanes (z = y)

26. Random poly(dimethyl-co-hydridomethyl-co-cyanopropylmethyl)siloxane29Si NMR

27. Observations • 50% of the hydridomethyl siloxanes in (1) were successfully hydrosilated with allyl cyanide as seen in (2). • Due to instrumental difficulties, the polymer was presumed to have slightly crosslinked under unexpectedly high thermal conditions. • A second 25g sample was made of (2) from (1).

28. (1) with Allyl Cyanide w/out catalyst at t=0 hours1H NMR 1.00 1.26

29. (1) with Allyl Cyanide w/ catalyst at t=11 hours1H NMR 1.00 0.18

30. Conclusions / Future Work • This reaction is very thermally sensitive. • Can successfully hydrosilate the hydridomethyl siloxanes • The second sample will reacted longer with more toluene and minimal Pt. cat. • Final product will be crosslinked and dispersed with Ag to make cured thin films. Relationship between volume fraction of Ag and electrical conductivity will be determined.

31. Outline • Cache: comparison of monomers’ ring strain. • MW Control: • Poly(dimethyl)siloxane (PDMS) • Poly(vinylmethyl)siloxane (PVMS) • Random poly(dimethyl-co-hydridomethyl-co-cyanopropylmethyl)siloxane • Hydroxybutyl-terminated PVMS • Future Work • Acknowledgments

32. Synthesis of Hydroxybutyl-terminated PVMS • The polymer was diluted with ethyl ether and washed with water until neutral (9 x 100mL H2O). Then rotovapped to remove excess ether. Vacuumed stripped any cyclics and H2O • Target MW: 2000 g/mol. Actual MW: ******GET GPC*******

33. Hydroxybutyl-terminated PVMS1H NMR 159.35 164.16 4.00

34. Hydroxybutyl-terminated PVMSGPC

35. Conclusions / Future Work • Preliminary analysis with 1H NMR shows purity but loss of MW control. • Will measure Tg and submit sample for 29Si NMR. • Hydroxybutyl endgroups will be further polymerized with caprolactone to produce a triblock copolymer.

36. Acknowledgements • Jennifer Hoyt • Dr. J. Riffle • Tom Glass • Riffle Group