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

refers to the use of external techniques to probe into the internal structure and properties of a material.

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

Mikhail Tswett, Russian, 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 graphin means to “ write ”

…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. Mobile phase Mobile phase is a liquid as water or dilute alcohol Separation mechanism Based on difference between the solutes molecular weights. Molecules will distribute themselves outside & inside the pores according to their size.

This type is also known as:

GPC can 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. Tensile strength Elastomer relaxation time Brittleness Toughness Softening temperature Cure time Elastic modulus Hardness Adhesive strength Impact strength

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

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

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. 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. The pore sizes of these particles are controlled and available in a range of sizes. SEC was first developed in 1955 by Lathe and Ruthven

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

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

High temperature GPC

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 sample PC Temperature Control (Furnace) Sensors Basic Principles of Thermal Analysis

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

The portion of material whose molecules are randomly oriented in space. Liquids and glassy or rubbery solids. Thermosets and some thermoplastics. The portion of material whose molecules are regularly arranged into well defined structures consisting of repeat units. Very few polymers are 100% crystalline. Polymers whose solid phases are partially amorphous and partially crystalline. Most common thermoplastics are semi-crystalline. 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. Amorphous Phase Crystalline Phase Semi-crystalline Polymers Melting

Semi-Crystalline (or Amorphous) Crystalline Phase melting temperature T m (endothermic peak) Amorphous Phase glass transition temperature (T g ) T g < T m Crystallisable polymer can crystallize on cooling from the melt at T c (T g < T c < T m )

Gas control Furnace Detectors Sample Reference Temperature controller Data acquisition Microvolt amplifier differential detector signal amplifier furnace temperature controller gas control device data acquisition device

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.

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

Exothermic upwards Endothermic downwards Y-axis – heat flow X-axis – temperature (and time) Desolvation Glass Transition (T g ) Crystallization (T c ) Melting (T m ) Decomposition H2OH2O Temperature ( o C) Typical Features of a DSC Trace

Heat Flow (W/g) Temperature (°C) cooling first heating second heating DSC Curve : Heat/Cool/Heat

Onset = Melting point (mp) Heat of fusion (melting) = integration of peak Temperature ( o C)

Temperature (°C) DSC Heat Flow (W/g) 10mg 4.0mg 15mg 1.7mg 1.0mg 0.6mg Indium at 10°C/minute Normalized Data Onset not influenced by mass

A technique measuring the variation in mass of a sample undergoing temperature scanning in a controlled atmosphere Thermobalance allows for monitoring sample weight as a function of temperature The sample hangs from the balance inside the furnace and the balance is thermally isolated from the furnace

Gas IN

Temperature Poly(PMDA-ODA-TMAc) Poly(PMDA-ODA-TPC) Poly(PMDA-ODA-IPC) % °C Nitrogen IDT Poly(PMDA-ODA-TMAc) Poly(PMDA-ODA-TPC) Poly(PMDA-ODA-IPC Temperature % °C Oxygen IDT - Initial decomposition Temp CD - Complete decomposition CD Data : Weight Vs Time Weight Vs Temperature Weight Loss

Weight Loss (%) Temperature ( o C) Step-I Step-II Step-III

UVX-raysIR  -rays RadioMicrowave ~10 -4 > 300~10 -6 Visible ~10 15 ~10 13 ~10 10 ~10 5 ~10 17 ~ nm1000 nm 0.01 cm 100 m~0.01 nm~.0001 nm nuclear excitation (PET) core electron excitation (X-ray cryst.) electronic excitation (p to p*) molecular vibration molecular rotation Nuclear Magnetic Resonance NMR The entire electromagnetic spectrum is used by chemists:

A molecule such as H 2 O will absorb infrared light when the vibration (stretch or bend) results in a molecular dipole moment change

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

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

O  H single bond N  H single bond C  H single bond C ≡ C C ≡ N C=O C=N C=C C  C C  N C  O Fingerprint Region Bonds to H Triple bonds Double bonds Single Bonds 4000 cm cm cm cm cm -1 The four primary regions of the IR spectrum

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 Non-porous solid Low specific surface area Low specific pore volume Porous solid High specific surface area High specific pore volume

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

2 nm50 nm Micropores Mesopores Macropores Zeolite, Activated carbon, Metal organic framework Mesoporous silica, Activated carbon Sintered metals and ceramics 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 Size of Pores (IUPAC Standard)

Gas adsorption Gas adsorption Small angle Neutron scattering Small angle X-ray scattering SEM TEM Mercury Porosimetry Techniques

Typical Pore Structure

Gel permeation chromatography (GPC) is a type of size exclusion chromatography (SEC), that separates analytes on 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. IR spectroscopy used to identify and study chemical structure of material in the Infra red region Porous material : micropores, mesopores and macropores