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Model polymer nanocomposites to study confinement effects in real systems
Miral Shah Course: Thermodynamics and kinetics of confined fluids Thank you for your kind introduction. My name is Miral Shah and I am pursuing PhD in chemical engineering at Texas A & M University. Today I am going to talk about the role of sodium formate in ZIF film fabrication. (Zeolitic Imidazolate framework) Instructor: Prof. Perla B. Balbuena Texas A&M University College Station Fall 2011
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Northwestern University, USA
Model polymer nanocomposites provide an understanding of confinement effects in real nanocomposites Nature materials: 2007 Authors: PERLA RITTIGSTEIN, RODNEY D. PRIESTLEY, LINDA J. BROADBELT1 AND JOHN M. TORKELSON Northwestern University, USA
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Outline Motivation Terms and definitions
Tg characterization using Fluorescence Model polymer nanocomposites Summary I am first going to talk about what are ZIF materials, their applications as gas separation membranes. The current fabrication techniques to make these membranes, the limitations of current technique. Then I will introduce you to our new one step insitu method which involves sodium formate. Then I will focus on the role of sodium formate in our method and finally summarize my results 2/21
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Polymer nanocomposite
Motivation Inorganic nanoparticles dispersed in polymer matrix Nanoparticles: High surface area Enhancement in properties Toughness Conductivity Permeability Applications: Membranes , fuel cells Polymer nanocomposite
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Motivation Enhancement in properties Determined by:
Toughness Conductivity Permeability Determined by: Interfacial interactions Interfacial area Internanofiller distance distribution Polymer nanocomposite Depend on nanofiller dispersion
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Challenges Analysis using conventional techniques like FTIR, XRD becomes complex Spacing determination using SEM, TEM etc. can de challenging Also experimental determination interfacial interaction is difficult Change in glass transition Tg can be used to study the interaction Strength of interaction will vary with interparticle distance
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Outline Motivation Terms and definitions
Tg characterization using Fluorescence Model polymer nanocomposites Summary I am first going to talk about what are ZIF materials, their applications as gas separation membranes. The current fabrication techniques to make these membranes, the limitations of current technique. Then I will introduce you to our new one step insitu method which involves sodium formate. Then I will focus on the role of sodium formate in our method and finally summarize my results 2/21
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Glass transition temperature (Tg)
Glass transition temperature is the critical temperature at which the material changes its behavior from being 'glassy' (hard and brittle) to being 'rubbery‘ (elastic and flexible) In nanofillers, Tg ↓ when polymer-nanofiller interfaces give rise to free surfaces Tg ↑ for wetted surface with attractive interactions
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Physical ageing Physical ageing: change in properties as a function of annealing time below Tg that accompanies spontaneous relaxation of non equilibrium glass towards metastable equilibrium amorphous state. Physical ageing in bulk and confined systems Increase in density with time Suppression of change in properties for confined systems
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Outline Motivation Terms and definitions
Tg characterization using Fluorescence Model polymer nanocomposites Summary I am first going to talk about what are ZIF materials, their applications as gas separation membranes. The current fabrication techniques to make these membranes, the limitations of current technique. Then I will introduce you to our new one step insitu method which involves sodium formate. Then I will focus on the role of sodium formate in our method and finally summarize my results 2/21
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Tg determination using fluoresence
Incorporate a fluorescent dye in trace amounts in the sample Collect Fluorescence emission spectrum
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Tg determination using fluoresence
Ellison et al., 2002
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Tg determination using fluoresence
Thick polystyrene film with Pyrene (487nm) Thin polystyrene film with Pyrene (24nm) Ellison et al., 2002
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Challenges in using Tg for real nanocomposites
Wide distribution of interparticle distance is determined by dispersion which will affect Tg Neighboring particles within a radius to nm could affect the interactions and therefore the Tg.
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Outline Motivation Terms and definitions
Tg characterization using Fluorescence Model polymer nanocomposites Summary I am first going to talk about what are ZIF materials, their applications as gas separation membranes. The current fabrication techniques to make these membranes, the limitations of current technique. Then I will introduce you to our new one step insitu method which involves sodium formate. Then I will focus on the role of sodium formate in our method and finally summarize my results 2/21
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Model polymer nanocomposite
Silica = Polymer Silica 2 Tg + 25K Polymer film spin coated on silica Consolidated film with constant interlayer distance
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Tg for Model polymer Nanocomposite
P2VP between silica surfaces PMMA between silica surfaces
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Tg for polymer nanocomposite
P2VP PMMA Attractive interactions, H-bonding PS Vander Waal’s interaction, hydrophobic interaction ΔTg PMMA = 5K , ΔTg P2VP = 10K
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Model polymer Nanocomposite
Silica = Polymer Silica 130 nm 300 nm P2VP model nanocomposites PMMA model nanocomposites
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Physical aging behavior
Physical aging behavior is similar for model and real nanocomposite Bulk P2VP film 0.4 vol% silica- P2VP nanocomposite 300 nm P2VP nanocomposite
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Outline Motivation Terms and definitions
Tg characterization using Fluorescence Model polymer nanocomposites Summary I am first going to talk about what are ZIF materials, their applications as gas separation membranes. The current fabrication techniques to make these membranes, the limitations of current technique. Then I will introduce you to our new one step insitu method which involves sodium formate. Then I will focus on the role of sodium formate in our method and finally summarize my results 2/21
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Summary Silica = Polymer Silica For same loading, “average effective” interparticle distance can be different for different systems (for 0.4vol%, for P2VP = 300nm and PMMA = 130nm) due to difference in distribution Model nanocomposites provide valuable insight about dependence of Tg on interparticle distance Can be extended further to understand behaviors like physical aging.
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Future prospects Silica = Polymer Silica Model nanocomposites can be used to rationally design new polymer nanocomposite systems with significantly enhanced interfacial properties By extending the confinement effects to the scale of 500nm, understanding and controlling confinement behavior becomes feasible experimentally Also the technique is relatively very simple to use
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Motivation Properties enhanced: Complex function of:
Conductivity toughness permeability Complex function of: Polymer nanocomposite Interfacial interactions Interfacial area Internanofiller distance distribution Depend on nanofiller dispersion: Fundamental understanding of their effect on properties is difficult Model nanocomposite to understand the effect of these on Tg and aging Tg + 25K 2 Polymer film spin coated on silica Consolidated film with constant interlayer distance
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Model Quantitative determination of silica interlayer dependence on Tg. Wide distribution of interparticle distances Tg affected by the number of nanoparticles within a radius of tens to hundreds of nm. Free surface removal by silica interface. Model nanocomposite
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Silica nanoparticles = 10-15nm
Temperature dependence of fluorescence intensity BPD doped 0.4 vol% silica-PMMA nanocomposite BPD doped Bulk PMMA film ΔTg = 5 K Silica nanoparticles = 10-15nm Scale: 100 nm PMMA structure Tg enhanced due to attractive polymer nanoparticle interfacial interactions
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Deviations from Tg bulk as a function of silica nanofiller content
P2VP PMMA Attractive interactions, H-bonding PS Vander Waal’s interaction, hydrophobic interaction ΔTg PMMA = 5K , ΔTg P2VP = 10K
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Tg deviaton dependence on thickness
P2VP supported films Interfacial area to volume ratio increases as thickness decreases Replacement of the free surface in films by a silica interface (model nanocomposites) with attractive interfacial interactions leads to an increase in the length scale of Tg-confinement
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Tg deviation as a function of thickness
130 nm 300 nm P2VP model nanocomposites PMMA model nanocomposites
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Intensity as a function of Physical ageing time
indicate that interfacial interactions that yield significant increases in Tg in nanocomposites may yield much more significant effects on other glassy behaviour: physical ageing Bulk P2VP film 0.4 vol% silica- P2VP nanocomposite 300 nm P2VP nanocomposite
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Research objective Understanding the interface between Nanoporous Inorganic Materials and Polymer. Quantify the interface parameters Interface thickness Interaction Type of bonding of the polymer Polymer chain relaxation sieve polymer Rigidified polymer interface
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How do we do that ? Step 1: Porous oxides on glass : Spin coat/ manual asembly Porous oxides (mesoporous silica/zeolite) Glass Step 2: Spin coat polymer on porous oxides Polymer Porous oxides (mesoporous silica/zeolite) Glass Step 1 & 2: Characterization and thickness by XRD, SEM, Ellipsometer Step 3: Bring two films in close contat and anneal Polymer Glass Porous oxides (mesoporous silica/zeolite) Porous oxides (mesoporous silica/zeolite) Glass Raman and Fluorescence spectroscopy to measure interface parameters
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Outline Introduction One step in situ synthesis method
ZIFs as candidates for gas separation membranes Current membrane fabrication techniques and their limitations One step in situ synthesis method Role of sodium formate Summary I am first going to talk about what are ZIF materials, their applications as gas separation membranes. The current fabrication techniques to make these membranes, the limitations of current technique. Then I will introduce you to our new one step insitu method which involves sodium formate. Then I will focus on the role of sodium formate in our method and finally summarize my results 2/21
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