New Hydrophilic Polymeric Coupling Agents Derived...
Transcript of New Hydrophilic Polymeric Coupling Agents Derived...
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