TY - JOUR
T1 - Surface science of elastomeric coatings prepared from α,ω-dihydroxypoly(dimethylsiloxane) and the ethoxysiloxane mixture `ES40'
AU - Uilk, Janelle
AU - Bullock, Steve
AU - Johnston, Erika
AU - Myers, Sharon A.
AU - Merwin, Larry
AU - Wynne, Kenneth J.
PY - 2000/11/14
Y1 - 2000/11/14
N2 - Hybrid poly(dimethylsiloxane) networks have been prepared with the ethoxysiloxane mixture `ES40' that acts as a cross-linker and siliceous domain (SD) precursor through sol-gel chemistry. ES40, with an approximate formula (SiO(OEt)2)n, is a mixture of oligo-ethoxysiloxanes that is much less volatile than tetraethoxysilane (TEOS) and provides hybrid elastomeric coatings of reproducible composition. With SiOEt from ES40 and SiOH from HO(Me2SiO)nH, compositions with SiOEt/SiOH ratios from 5 to 35 (ES40-5x-ES40-35x) were prepared. Solid-state 29Si NMR spectroscopy was used to determine the relative amounts of PDMS and SD in the hybrid elastomers. The relative amounts of Q2, (≅SiO)2Si(OH)2; Q3, (≅SiO)3Si(OH); and Q4, (≅SiO)4Si, in the SD were estimated by deconvolution of the 29Si NMR peaks. Both light microscopy and tapping mode atomic force microscopy (TM-AFM) show that PDMS-SD compositions `5x' and higher slowly develop `island-like' surface features while stored at ambient conditions. After 1 month cure, PDMS-SD surface features are ≤1 μm, while after 6 months feature size is broadly distributed up to approximately 10 μm. In contrast, surface features developed quickly (24 h) with previously reported PDMS-FSD hybrids, where FSD is fluorinated siliceous domain, from (tridecafluoro-1,1,2,2-tetrahydrooctyl)triethoxysilane. AFM experience demonstrates that PDMS-SD surface features are often poorly adherent and easily moved compared to the robust phase-separated surface structure of PDMS-FSD materials. Differing dynamic contact angle (DCA) analysis protocols with water as the interrogating fluid show that water contamination affects force vs distance curve (fdc) data for PDMS-SD hybrids. Intrinsic wetting behavior for PDMS-SD hybrids is reproduced only with a protocol where clean water is used for each DCA cycle. The stability in water of PDMS-SD materials is strongly compositionally dependent. Over a period of 70 days, the ES40-14x composition showed the greatest resistance to mass loss with a mass loss rate of 0.08 wt%/month.
AB - Hybrid poly(dimethylsiloxane) networks have been prepared with the ethoxysiloxane mixture `ES40' that acts as a cross-linker and siliceous domain (SD) precursor through sol-gel chemistry. ES40, with an approximate formula (SiO(OEt)2)n, is a mixture of oligo-ethoxysiloxanes that is much less volatile than tetraethoxysilane (TEOS) and provides hybrid elastomeric coatings of reproducible composition. With SiOEt from ES40 and SiOH from HO(Me2SiO)nH, compositions with SiOEt/SiOH ratios from 5 to 35 (ES40-5x-ES40-35x) were prepared. Solid-state 29Si NMR spectroscopy was used to determine the relative amounts of PDMS and SD in the hybrid elastomers. The relative amounts of Q2, (≅SiO)2Si(OH)2; Q3, (≅SiO)3Si(OH); and Q4, (≅SiO)4Si, in the SD were estimated by deconvolution of the 29Si NMR peaks. Both light microscopy and tapping mode atomic force microscopy (TM-AFM) show that PDMS-SD compositions `5x' and higher slowly develop `island-like' surface features while stored at ambient conditions. After 1 month cure, PDMS-SD surface features are ≤1 μm, while after 6 months feature size is broadly distributed up to approximately 10 μm. In contrast, surface features developed quickly (24 h) with previously reported PDMS-FSD hybrids, where FSD is fluorinated siliceous domain, from (tridecafluoro-1,1,2,2-tetrahydrooctyl)triethoxysilane. AFM experience demonstrates that PDMS-SD surface features are often poorly adherent and easily moved compared to the robust phase-separated surface structure of PDMS-FSD materials. Differing dynamic contact angle (DCA) analysis protocols with water as the interrogating fluid show that water contamination affects force vs distance curve (fdc) data for PDMS-SD hybrids. Intrinsic wetting behavior for PDMS-SD hybrids is reproduced only with a protocol where clean water is used for each DCA cycle. The stability in water of PDMS-SD materials is strongly compositionally dependent. Over a period of 70 days, the ES40-14x composition showed the greatest resistance to mass loss with a mass loss rate of 0.08 wt%/month.
UR - http://www.scopus.com/inward/record.url?scp=0034316263&partnerID=8YFLogxK
U2 - 10.1021/ma000023y
DO - 10.1021/ma000023y
M3 - Article
AN - SCOPUS:0034316263
SN - 0024-9297
VL - 33
SP - 8791
EP - 8801
JO - Macromolecules
JF - Macromolecules
IS - 23
ER -