1. Introduction to polymer science.
Definitions of polymer, monomer, macromolecule, homopolymer, copolymer. Plastics and their relevance. Natural, synthetic and artificial polymers. Inorganic polymers. Classification of polymers on the basis of the chemical structure they belong to. Molecular architectures. Classification of copolymers (statistical, block, graft, alternating) and their relevance. Phase separation in block copolymers. Regioisomerism, geometric isomerism, configurations and conformations of polymers. Polymeric architectures. Definition of molecular weight of a polymer; definition of numeral and weight average and molecular weight distribution. Examples of calculation of the number and weight average molecular weights of polymers.
2. Polymerization with a step-wise mechanism.
Classification of monomers polymerizable by this mechanism: bifunctional monomers of type A-B; mixtures of monomers with two identical functions, A-A / B-B. Polycondensation and polyaddition polymers structures of industrial interest. Qualitative dependence of the degree of polymerization on the conversion and ratio of the reactants. Use of reaction catalysts. Polymerization kinetics. Dependence of the average degree of polymerization on the reaction parameters (conversion, monomer ratio, presence of monofunctional reagents). Kinetics of step-wise polymerization in the presence and absence of catalysts.
3. Polymerization with radical mechanism.
Classification of polymerizable vinyl monomers; because olefins do not normally polymerize with a radical mechanism. General characteristics of the process: a) polymerization with chain mechanism; b) stage of initiation, propagation and termination; c) non-stereospecific addition reactions. Thermodynamics of polymerization reactions with radical mechanism: exothermic reactions. Concentrations of reactive species. Initiation reaction by: a) thermal, photochemical or electrochemical decomposition of initiators; b) spontaneous dissociation of the monomer (styrene and methyl methacrylate); c) redox reactions. Chain transfer reaction and control of the molecular weight of polymers. Polymerization kinetics and stationary stage hypothesis. Dependence of the numeral average degree of polymerization on the reaction parameters. Chain transfer: Mayo equation. Inhibitors and retardants. Self-acceleration effect. Definition of "ceiling temperature".
4. Industrial polymerization processes with radical mechanism
Solution and bulk polymerization. Suspension polymerization: description of the process and role of the protective colloid. Influence of process parameters. Molecular weight trend compared to mass polymerization. Emulsion polymerization: definition of surfactant, micelle, micellar critical concentration, emulsion. Heterophasic system in emulsion polymerization processes: monomer in solution, monomer drops, micelles and polymer particles. Site of polymerization and diffusive control of the process. Phases of the polymerization rate. Dependence of the numeral average degree of polymerization on the surfactant concentration.
5. Polymerizations with ionic mechanism.
Polymerizable monomers with ionic mechanism. Main characteristics of polymerization mechanisms with ionic intermediates: solvent effect, reaction rate, absence of the term reaction. Polymerization with cationic mechanism: classification of the main classes of initiators, termination reaction and chain transfer. Polymerization with anionic mechanism: carbanionic initiators; absence of the chain transfer and termination reaction. Living nature of polymerization with anionic mechanism. Dependence of the molecular weight on the monomer / initiator ratio.
7. Determination of the molecular weights of polymers: size exclusion chromatography.
Definition of Size Exclusion Chromatography: Gel Permeation Chromatography and Gel Filtration Chromatography. Physical principle of operation: nature of the stationary phase; fractionation of polymers with wide molecular weight distribution on the basis of the ordinamic volume of the macromolecules in the eluent. Calibration of a SEC column system: nature of standards and calibration curve. Limitations in the use of standards with a different chemical structure than the analyte. Calculation of the numeral and weight average. Effect of the solvent: viscosity of the solvent, interaction of the solvent with the solute. Effect of eluent flow.
8 - Amorphous state of polymers.
Definition of amorphous phase: absence of geometric order and molecular symmetry, absence of X-ray diffraction spectra. Amorphous polymers as homogeneous and isotropic materials. Definition of glass transition and glass transition temperature, Tg. Meaning of Tg: correlation with molecular dynamics; free volume. Tg as a kinetic and non-thermodynamic transition. Gummy and glassy amorphous state. Definition of hard and brittle polymers and viscoelastic polymers. Classification of the structural factors that influence the Tg value: internal factors (cohesive energy, polarity, structural flexibility) and external factors (presence of plasticizers, degree of crosslinking, presence of comonomer units). Examples of Tg values of commercial polymers. Physical aging of polymers.
9. Crystalline state of polymers.
Definition of crystalline phase: geomentric order and molecular symmetry; X-ray diffraction spectra,. Definition of fusion and variation of the thermodynamic state functions at the fusion. Melting temperature (Tm = melting temperature). Structural requirements for a polymer to crystallize: regular primary structure, cofigurational and conformational order. Morphology classification of polymeric crystals: lamellae, spherulites, kebabs. Description of the lamellae: dimensions, geometry, and molecular folds; tie molecules. Spherulites: geometry, symmetry and coexistence with the amorphous phase. Growth of spherulites from lamellae. Structural hierarchy in spherulites. Examples of Tm values of commercial polymers. Correlation between Tm and structural flexibility.
1. Synthesis of polyhexamethylene maleate by step polymerization.
2. Synthesis of a polyamidoamine by step polymerization.
3. Synthesis of polystyrene by radical mechanism polymerization with suspension process.
4. Synthesis of polyethylacrylate by polymerization with anionic mechanism.
5. FT-IR and NMR analysis of the synthesized polymers.
6. Determination of the molecular weights of the synthesized polymers.
Prerequisites for admission
Basic knowledge of organic chemistry.
· Course slides and dedicated videos in the case of the laboratory course, available at https://eranuccicm.ariel.ctu.unimi.it/v5/home/Default.aspx
· "Textbook of polymer science" Fred W. Byllmeyer, Wiley.
· "Chemistry and Physics of Modern Materials", Third Edition
J.M.G. Cowie, Valeria Arrighi, CRC Press.
Assessment methods and Criteria
The exam will consist of an oral interview lasting 30-35 minutes. The exam calendar will be published on the University intranet.
The score will vary between 18 and 30 out of 30 and will be proportional to the number of correct answers.
The oral interview will aim to ascertain the achievement of the expected learning outcomes in terms of knowledge and understanding. The evaluation criteria will focus on the student's ability to answer open short answer questions (DRAB) on all topics covered in both the theoretical section and in the laboratory module of the course. The exam will begin by discussing the topics covered in the laboratory module.
· Description of the synthetic schemes of the reactions performed and the experimental conditions adopted.
· Discussion of the IR and NMR spectra provided.
· Description of the method used to determine the molecular weight values of the synthesized polymers by SEC analysis.
THEORETICAL MODULE: questions will be formulated regarding the various sections dealt with.
· General definitions and introductory concepts of polymer chemistry.
· Description of the different reaction mechanisms considered, particularly defining the families of polymerizable monomers, the stages of initiation, growth and termination of the macromolecular chain, the trend of the degree of polymerization with conversion, the control of molecular weights, the chain transfer mechanism.
· Stereochemistry control in the case of the mechanism with coordinated insertion.
· Definition of the main features of the amorphous and crystalline state forms of polymers.
· Description of the morphology of crystalline polymers.
· Definition of the main transition temperatures of the amorphous state and of the crystalline state of polymers. Knowledge of the glass transition and melting temperatures of the main commercial polymers considered in the course.