The Power of Thermodynamics in the Characterization of Materials Zeki Y. Al-Saigh Department of Chemistry Buffalo State, State University of New York 1300 Elmwood Avenue Buffalo, N.Y., USA

Outline Background about Materials Techniques used in the Characterization The Physics of Characterization Results Derived from the Speaker’s Research: Polymers, Polymer Blends, Conducting Polymers, Biodegradable Polymers.

Characterization of Materials Obtaining information on the physical and chemical properties of materials, such as: Mechanical Properties Thermal Properties Interaction Forces Among Molecules Crystallinity Molecular Weight Diffusion of Gases into Layers

Materials: Can be anything which exists in nature: Plastics (polymers), synthetic and natural Rubbers Alloy and Ceramics Oil, Coal and carbon fibers Powders and clay Food

Polymer Blends –A new class of materials is always needed to replace heavy metal alloys.

Polymer Blends Blending of polymers is a fast and inexpensive route to obtaining a new class of materials Z.Y.Al-Saigh, International J. of Polymer Analysis and Characterization, 3, (1997) FOR MORE INFO on IGC of polymer blends...

Polymer Blends Solubility of Polymers is the key term in polymer characterization

Polymer Blends A pair of polymers may be: Compatible (soluble) Incompatible (insoluble) Partially compatible Z.Y.Al-Saigh, Trends in Polymer Science, 5, 97 (1997) FOR MORE INFO on IGC of polymer blends...

Present Techniques Available Glass transition temperature Thermal & mechanical NMR Electron spin resonance Solvent vapor sorption heat of mixing Small angle light & X-ray scattering Small angle neutron scattering Inverse gas chromatography

Unfortunately Most of these techniques are beset by a number of technical difficulties

For Example Vapor sorption method takes a long time for the establishment of equilibrium between the vapor and the polymer Neutron scattering uses modified dueterated polymers which are chemically different from the parent polymer

Gas Chromatography As an alternative method for polymer analysis and characterization Al-Saigh, Z.Y. and Guillet, J., in “Inverse Gas Chromatography in Analysis of Polymers and Rubbers”, Invited Chapter. Encyclopedia of Analytical Chemistry: Instrumentation and Applications, R. Meyers, Editor, PP , John Wiley & Sons Ltd, Chichester, (2000).

Gas Chromatography is: A technique by which a mixture of components can be separated, analyzed and quantified. It works on the principle of interactions of two phases; stationary and mobile. The stationary phase contains material with active interaction sites, such as sand. The mobile phase is the vapor of the mixture to be analyzed.

Inverse Gas Chromatography The method is called inverse gas chromatography because the stationary phase (polymers or polymer blends) is of interest, unlike the traditional GC method.

Thermodynamics of IGC

Inverse Gas Chromatography IGC may provide data about: Polymer-solvent interaction Homopolymers Blends Diffusion Glass Transition

Current Use of IGC 1. Interaction parameters of polymer- solvent systems 2. Interaction parameters of polymer- polymer systems 3. Solubility parameters and weight fraction coefficients 4. Molar heat, free energy, and entropy of mixing 5. Molar heat, free energy, and entropy of sorption

6. Degree of crystallinity of semicrystalline polymers 7. Diffusion of gases and liquids into the polymer layer 8. Glass transition and melting temperatures 9. Surface energy of solids 10.Detection of melting point depression of a polymer blend as an indicator of miscibility

Background: Thermodynamics of IGC

Thermodynamics of IGC

Heats of the Mixing Process

Thermodynamics of Polymer Blends Miscibility

Blend of semicrystalline diluent Are interesting systems for the characterization by inverse gas chromatography C.T.Chen and Z.Y.Al-Saigh, Macromolecules, 24, 3788 (19910 FOR MORE INFO...

Blend of semicrystalline diluent Two blend systems were studied: Poly(vinylidene fluoride)-poly(ethyl methacrylate) [PVF2-PEMA] Poly(vinylidene fluoride)-poly(vinyl methyl ketone) [PVF2-PVMK]

Blend of semicrystalline diluent Above PVF2 m.p., both polymers are at melt Below PVF2 m.p., two retention mechanisms are expected: Adsorption of solutes on crystal surfaces Absorption of solutes by the amorphous layer

Blends of semicrystalline diluent

Blend of Semicrystalline Diluent

Conducting Polymers: The unique properties have lead to an interest in the potential use of PANI as a new class of conductors. This interest was generated due to the relative ease of synthesis, low cost, and the stability of PANI in the air. However, the insulating form a PANI, polyaniline emeraldine base (PANI-EB) suffers from the limited solubility in organic solvents.

Dependence of V g of Acetates-PANI-EB on Temperature (130 – 170 ° C)

Dependence of V g of Alkanes-PANI-HEBSA on Temperature (80 – 130 ° C)

Table III : Interaction Parameters of Alkanes at a Temperature Range ° C for 7% PANI-EB

Table IV : Interaction Parameters of Alkanes at a Temperature Range ° C for 7% PANI-HEBSA

Table V : Molar Heat of Sorption,   s, of both PANI-EB and PANI-HEBSA

Surface Energy

Table VI : Dispersive Surface Energies of PANI-EB and PANI-HEBSA and  CH2

Surface Energy (mJ/m A 2) Surface Energies of Polymers Polymer PEO PVMK Hg PVC PMMA Polypropylene Polyurethane Polyethylene doped PPY Comparative Data on Surface Energy of Several Polymers

Inverse Gas Chromatography of Polyaniline REFERENCES: By Ali Al-Ghamdi & Zeki Y. Al- Saigh, Journal of Chromatography, A, 969, (2002) 229. Al-Saigh & Guillet, Encyclopedia of Analytical Chemistry, Volume 9, Page 7759 (2000), Wiley.

Application of IGC to Biodegradable Polymers Fibers acid/base interaction potential Wettability test (determination of water sorption isotherm) Surface adsorption characterization Thermodynamic studies wood-polymer interface studies

Current Research Characterization of Starch-Based Polymers such as Amylopectin Amylopectin is known to be mechanically weak. Blending Amylopectin with another biodegradable polymer may improve the mechanical properties.

Amylopectin – Alkanes Syatems

Amylopectin – Alcohols Syatem

Effect of Temperature on the Interaction Parameters, χ 12

Effect of Number of Carbon on the Interaction Parameters, χ 12

Degree of Crystallinity of Amylopectin

The dispersive Surface Energy, γ s d, of Amylopectin Temperature, o Cγ CH2, mJ/m 2 γ s d, mJ/m

Latest Applications of IGC Amorphous, co-polymer and blends Semicrystalline polymers and blends Inorganic polymers Amorphous-plasticizer blend Conducting polymers Rubbers Coal and carbon fibers Powders and clay Food