Characterization of Polymers

1. Characterization of Polymers D. JAGAN MOHAN New Technology Research Centre University of West Bohemia Plzen, Czech Republic

2. CHARACTERIZATION….? TMA HPLC DMA XRD NMR GPC SAXS refers to the use of external techniques to probe into the internal structure and properties of a material. IR TGA Polymer DSC SEM TEM

3. GEL PERMEATION CHROMATOGRAPHY DIFFERENTIAL SCANNING CALORIMETRY THERMOGRAVEMETRIC ANALYSIS INFRA RED SPECTROSCOPY POROSITY TECHNIQUES FOR PROSITY ANALYSIS

4. Chromatography Mikhail Tswett, Russian, 1872-1919 Botanist • In 1906 Tswett used to chromatography to separate plant pigments • He called the new technique chromatography because the result of the analysis was 'written in color' along the length of the adsorbent column • Chroma means “color” and graphinmeans to “write”

5. Chromatography …is a technique used to separate and identify the components of a mixture. Works by allowing the molecules present in the mixture to distribute themselves between a stationary and a mobile medium. Separation mechanism Based on difference between the solutes molecular weights. Mobile phase Mobile phase is a liquid as water or dilute alcohol Molecules will distribute themselves outside & inside the pores according to their size.

6. Gel Permeation Chromatography (GPC) This type is also known as: Size Exclusion Chromatography (SEC) Molecular Exclusion Chromatography (MEC) Molecular Sieve Chromatography (MSC) Gel Filtration Chromatography (GFC) Gel Chromatography

7. Gel Permeation Chromatography……? • GPCcan determine several important parameters. These include number average molecular weight, weight average molecular weight, and the most fundamental characteristic of a polymer its molecular weight distribution. • These values are important, since they affect many of the characteristic physical properties of a polymer. Adhesive strength Tensile strength Elastomer relaxation time Cure time MWCO Brittleness Elastic modulus Hardness Impact strength Softening temperature Toughness

8. GPC "Size Exclusion" chromatography Polymer solution • Molecular weight distribution small molecules Column medium molecules Large molecules • Number average Molecular weight Separation based on Size • Weight average Molecular weight

9. Size exclusion chromatography Large particles cannot enter gel and are excluded. They have less volume to traverse and elute Small particles can enter gel and have more volume to traverse. They elute later chromatogram flow time

10. How GPC works SEC was first developed in 1955 by Lathe and Ruthven GPC separates molecules in solution by their "effective size in solution." To prepare a sample for GPC analysis the polymer sample is first dissolved in an appropriate solvent. Inside the gel permeation chromatograph, the dissolved sample is injected into a continually flowing stream of solvent (mobile phase). The mobile phase flows through millions of highly porous, rigid particles (stationary phase) tightly packed together in a column. The pore sizes of these particles are controlled and available in a range of sizes.

11. Schematic of a basic Gel permeation chromatograph sample Data system Solvent delivery system detector(s) injector Column(s) Solvent supply Mobile phase

12. Size Exclusion Chromatography Large molecules are excluded Small molecules penetrate pores of particles Polymer – Dissolving in solvent Membranes – Passed through std. sol. MWCO (Molecular weight Cut-Off)

13. GPC Instrument High temperature GPC

14. GPC Analysis

15. Basic Principles of Thermal Analysis Modern instrumentation used for thermal analysis usually consists of the following parts: • sample holder/compartment for the sample • sensors to detect/measure a property of the sample and the temperature • an enclosure within which the experimental parameters (temperature, speed, environment) may be controlled • a computer to control data collection and processing Temperature Control (Furnace) sample PC Sensors

16. Introduction to DSC two calorimeters (for sample and reference) with the same heat transfer behavior (for compensation purpose) Differential the common operation mode is to run temperature or time scans Scanning Calorimeter instrument to measure heat or heat flow

17. DSC: Terminology The portion of material whose molecules are randomly oriented in space. Liquids and glassy or rubbery solids. Thermosets and some thermoplastics. Amorphous Phase The portion of material whose molecules are regularly arranged into well defined structures consisting of repeat units. Very few polymers are 100% crystalline. Crystalline Phase Polymers whose solid phases are partially amorphous and partially crystalline. Most common thermoplastics are semi-crystalline. Semi-crystalline Polymers The endothermic transition upon heating from a crystalline solid to the liquid state. This process is also called fusion. The melt is another term for the polymer liquid phase. Melting

18. Thermoplastic Polymers Semi-Crystalline (or Amorphous) Crystalline Phase melting temperature Tm (endothermic peak) Amorphous Phase glass transition temperature (Tg) Tg < Tm Crystallisable polymer can crystallize on cooling from the melt at Tc (Tg < Tc < Tm)

19. Gas control A DSC apparatus is built around Furnace differential detector Sample Reference Detectors Temperature controller temperature controller signal amplifier furnace gas control device Data acquisition Microvolt amplifier data acquisition device

20. Differential Scanning Calorimetry Sample Pan Pan sealed DSC measures the temperatures and heat flows associated with transitions in materials as a function of time and temperature in a controlled atmosphere. These measurements provide quantitative and qualitative information about physical and chemical changes that involve endothermic or exothermic processes, or changes in heat capacity.

21. Typical DSC Curve of a Thermosetting Polymer Oxidation Crystallization Cross - Linking (Cure) > exothermic - Glass Transition Heat Flow Melting Temperature

22. Typical Features of a DSC Trace Exothermic upwards Endothermic downwards H2O Melting (Tm) Crystallization (Tc) Glass Transition (Tg) Desolvation Decomposition Y-axis – heat flow X-axis – temperature (and time) Temperature (oC)

23. 1.5 cooling 1.0 0.5 first heating Heat Flow (W/g) 0.0 second heating -0.5 -1.0 -1.5 0 40 80 120 160 200 240 Temperature (°C) DSC Curve : Heat/Cool/Heat

24. MELTING Onset = Melting point (mp) Heat of fusion (melting) = integration of peak Temperature (oC)

25. Influence of Sample Mass 0 Indium at Onset not 10°C/minute -2 influenced Normalized Data 15mg by mass 10mg DSC Heat Flow (W/g) 4.0mg -4 1.7mg 1.0mg 0.6mg -6 150 152 154 156 158 160 162 164 166 Temperature (°C)

26. Thermogravimetric Analysis (TGA) balance A technique measuring the variation in mass of a sample undergoing temperature scanning in a controlled atmosphere sample Thermobalance allows for monitoring sample weight as a function of temperature furnace The sample hangs from the balance inside the furnace and the balance is thermally isolated from the furnace purge gas

27. Balance Controller Weight Sample Temp. Furnace Temp. Power Temperature Programmer TGA INSTRUMENT Gas IN Sample Heater

28. TGA Curve

29. % % 100 80 80 60 60 40 40 20 Poly(PMDA-ODA-IPC) Poly(PMDA-ODA-IPC 20 Poly(PMDA-ODA-TPC) Poly(PMDA-ODA-TPC) Poly(PMDA-ODA-TMAc) 0 Poly(PMDA-ODA-TMAc) 0 100 200 300 400 500 600 700 800 °C 100 200 300 400 500 600 700 800 °C Temperature Temperature Nitrogen IDT TGA in Nitrogen and Oxygen atmosphere Weight Loss Weight Loss Oxygen CD Data : IDT- Initial decomposition Temp Weight Vs Time Weight Vs Temperature CD - Complete decomposition

30. Step by Step Decomposition Step-I Step-II Weight Loss (%) Step-III Temperature (oC)

31. IR Spectroscopy • The entire electromagnetic spectrum is used by chemists: Frequency, n in Hz ~1019 ~1017 ~1015 ~1013 ~1010 ~105 Wavelength, l ~.0001 nm ~0.01 nm 10 nm 1000 nm 100 m 0.01 cm Energy (kcal/mol) > 300 300-30 300-30 ~10-4 ~10-6 g-rays X-rays UV IR Microwave Radio Visible

32. Infrared Spectroscopy A molecule such as H2O will absorb infrared light when the vibration (stretch or bend) results in a molecular dipole moment change O O O H H H H H H Bend Asymmetric Stretch Symmetric Stretch

33. Infrared Spectra A molecule can be characterized (identified) by its molecular vibrations, based on the absorption and intensity of specific infrared wavelengths. Water O-H Bend O-H Stretching

34. IR spectra The Infrared region is divided into: near, mid and far-infrared. • Near-infrared refers to the part of the infrared spectrum that is closest to visible light and far-infrared refers to the part that is closer to the microwave region. • Mid-infrared is the region between these two

35. Infrared Group Analysis • The four primary regions of the IR spectrum • Single Bonds • Bonds to H • Double bonds • Triple bonds • CC • CN • CO • OH single bond • NH single bond • CH single bond • C=O • C=N • C=C • C ≡ C • C ≡ N • Fingerprint • Region 1600 cm-1 4000 cm-1 2000 cm-1 400 cm-1 2700 cm-1

36. What are Porous Materials……? Non-porous solid Low specific surface area Low specific pore volume Porous solid High specific surface area High specific pore volume Porous materials have highly developed internal surface area that can be used to perform specific function. Almost all solids are porous except for ceramics fired at extremely high temperatures

37. Concept of Porosity closed Inter-connected (open) Open pores are accessible whereas closed pores are inaccessible pores. Open pores can be inter-connected, passing or dead end. Passing (open) Dead end (open)

38. Size of Pores (IUPAC Standard) Macropores Mesopores Micropores Zeolite, Activated carbon, Metal organic framework Mesoporous silica, Activated carbon Sintered metals and ceramics 2 nm 50 nm Porous material are classified according to the size of pores: material with pores less than 2 nm are called micropores, materials with pores between 2 and 50 nm are called mesopores, and material with pores greater than 50 nm are macrospores

39. Techniques for Porosity Analysis Gas adsorption Gas adsorption Small angle Neutron scattering Mercury Porosimetry Techniques Small angle X-ray scattering TEM SEM

40. Pore Structure Typical Pore Structure

41. Conclusion Gel permeation chromatography (GPC) is a type of size exclusion chromatography (SEC), that separates analyteson the basis of size. DSC is a thermoanalytical technique in which the difference in the amount of heat required to increase the temperature of a sample and reference is measured as a function of temperature TGA is a type of testing performed on samples that determines changes in weight in relation to a temperature program in a controlled atmosphere. IRspectroscopy used to identify and study chemical structure of material in the Infra red region Porous material : micropores, mesopores and macropores

42. Thank U