new hydrophilic polymeric coupling agents derived...
TRANSCRIPT
Silicon Symposium
New Hydrophilic Polymeric Coupling Agents Derived from Epoxy Functional Monomers
Ferdinand Gonzaga, Jonathan Goff and Gerald L. Larson
Gelest, Inc.
Gelest - Enabling Your Technology
Coupling Agents
Molecules which have the ability to create a durable bond between organic and inorganic materials.
Silane coupling agents: Model structure:
(CH 2 ) n
R
Si
X X X
R: organofunctional group
Spacer
X: Hydrolyzable groups: • Alkoxy • Acyloxy • Halogen • Amine (cyclic azasilanes)
Properties of Coupling Agents
Control and tailor surface or interfacial properties of inorganic materials
Properties:
• Wettability: • Hydrophilicity • Hydrophobicity • Omniphobicity
• Adhesion • Ordering (monolayers) • Reactivity • Refractive Index
Substrates:
• Siliceous materials: •Silica •Glass
• Aluminium oxides • Zirconium oxides • Tin, Nickel Oxides • Titanium oxides • Boron, Iron and Carbon oxides
B. Arkles, Chemtech, 7(12), 766,1977.
Bonding Mechanism
Hydrolysis Condensation
Hydrogen Bonding
Bond Formation
Coating Degradation
• Hydrolytic stability of the oxane bond between silane and substrate
• Application in an aggressive environment (acidic/basic/saline)
(CH 2 ) n
R
Si
X X X Conventional Silane
• Gelest solution: dipodal silane coupling agents
Improved Stability from Dipodals
40
60
80
100
120
0 20 40 60 80 100 120 140 160 180
Stat
ic W
ater
Con
tact
Ang
le ,θ
(°)
t (days in 6 M HCl)
SiOC2H5
OC2H5OC2H5
Si SiOCH3
OCH3
OCH3OCH3H3CO
• Tighter networks • Up to X105 greater hydrolytic resistance
Multipodals coupling agents?
• Dipodals synthesis: • Synthetic challenges • Time consuming • Cost
• Polymerization of available monomers • Mild, tolerant to functional groups • Simple, cost-effective
Polymeric, multipodal coupling agents?
Polymerization of Epoxides
SiX3 SiX3
SiX3
R
R
R R
Ring Opening Epoxide Polymerization • Anionic ROP:
• Cationic ROP:
• Lewis Acid Catalyzed (Coordination catalyst):
• No strong nucleophile/electrophile • No formal charge • No hydrolytic conditions
Tris(pentafluorophenyl) Borane • Active at very low loadings • Robust and easy to handle (Air, Moisture) • Commercially available
• Widely used in Silicon chemistry:
• Dehydrogenative coupling of silanes and alcohols • Hydrosilylation of ketones • Piers-Rubinsztajn reaction
Proof of Principle Polymerisation
SIG5820.0
Conditions: Initiator (methallyl alcohol): 1 equiv. Monomer: 10 equiv. Catalyst: 0.8 mol% Slow monomer addition
Results: Mw:2,600g/mol Mn:1,702 Mw/Mn: 1.49 Yield: 96% Complete conversion (1H NMR)
Exotherm!
SIG5820.0
Conditions: Initiator (methallyl alcohol): 1 equiv. Monomer: 20 equiv. Catalyst: 0.8 mol% Slow monomer addition 2nd charge of catalyst required
Milder exotherm
Proof of Principle (2)
Results: Mw:2,391g/mol Mn:1,440 Mw/Mn: 1.66 Yield: 93%
Copolymerization with Trialkoxysilanes
Conditions: Initiator (methallyl alcohol): 1 equiv. Monomer: 20 equiv. (9:1 ratio) Catalyst: 0.8 mol% Slow monomer addition
Results: Mw:4,388g/mol Mn:2,334 Mw/Mn: 1.88 Yield: 85%
9 1
Triethoxysilyl groups unaffected during process
PEG as Polymerization initiator
Conditions: Initiator (methallyl alcohol): 1 equiv. Monomer: 6 equiv. (2:1 ratio) Catalyst: 0.8 mol% Slow monomer addition
Results: Mw:2,464 g/mol Mn: 1,388 Mw/Mn: 1.78 Yield: 86%
4 2
Access to functional block-copolymers
NMR Analysis
a
a b
b
c
c
d d
e, e’, h, h’
e
e e’
f
f’
g’
f, f’
g
g, g’
h
h’ e’
i
i
j
j
Epoxy-PEG monomers
Conditions: Initiator (methallyl alcohol): 1 equiv. Monomer: 20 equiv. (1:1 ratio) 60°C, Catalyst: 5 mol%
Results: Mw: 4,152 g/mol Mn: 1,269 Mw/Mn: 3.27 Yield: 78%
Need to optimize reaction conditions
10 10
Synthesis Conclusions • Epoxides efficiently polymerized by B(C6F5)3 • Polymerization orthogonal to Alkoxysilanes
• Access to various architectures/functionalities:
• Reaction sensitive to experimental conditions:
• Moisture • Induction time and exotherm variability • Discrepancy calculated/experimental MW
Polymeric Coupling Agents Efficiency
• Objective: assess wetting behavior of 3 PCA thin films. • Plan of Action:
• Design experimental procedure for surface modification • Treat BoroSilicate glass with PCA (3) • Analyze efficiency using Contact Angle measurements
PCA-TMS mPEG-PCA PCA-(PEG)m PCA-TMS
Experimental Procedure
• Borosilicate glass slide cleaning: Ethanol wash / Nitrogen dried • Acid Etch:
1. Glass slides dipped for 45minutes in 4% aqueous HCl 2. Rinse (DI / Ethanol / Acetone) 3. Nitrogen dried • Coating:
1. Glass slides dipped for one hour in reactive formulation (90% Ethanol, 5% Deionized Water, 5% PCA, 0.05% Acetic Acid) 2. Rinse (Ethanol) / Dry (N2) 3. Cure (80°C; 1 hour) 4. Cool down (dessicator) • Contact Angle measurement
Results
PCA-TMS mPEG-PCA
57
24
41
2121
30
0
10
20
30
40
50
60
PCA-TMS mPEG-PCACoupling Agent
Con
tact
Ang
le (D
egre
es)
WaterDiiodomethaneHexadecane
PCA-(PEG)m
Results
( 6 measurements averaged, 6 slides)
57
24
5
0
10
20
30
40
50
60
PCA-TMS mPEG-PCA PCA-(PEG)n
Coupling Agent
Cont
act A
ngle
(Deg
rees
)
Water
Super-wetting coupling agent
Conclusions / Future Work
• New synthetic route to polymeric coupling agents • Mild, versatile process
• Access to various architectures/functionalities
• Future work:
• Improve experimental conditions • Extend methodology to new monomers / initiators • Formulate new coatings • Durability tests