Information on the exercises and home assignments in polymer chemistry

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1 Polymer Chemistry Course, KTE 080, 2016 Patric Jannasch Information on the exercises and home assignments in polymer chemistry Polymer & Materials Chemistry

2 The exercises The exercises comprise 73 problems divided into seven chapters. Approximately 20 problems will be solved in connection to the lessons, the rest are for self-studies. Some exam problems from previous years are also among the exercises. We highly recommend that you attempt to solve some of the problems before submitting your home assignments. The lessons The exercises are organized as seminars during which you are expected to contribute actively. Prepare the seminars by reading the corresponding chapters in the literature (Cowie), and attempt to solve the listed problems beforehand. This will make the lessons more efficient and rewarding. Approximate time distribution Stepwise polymerization 2 h Chain polymerization by radical mechanism 4 h Copolymerization 2 h Polymers in solution, etc. 2 h Exam problems from previous years 2 h Sum: 12 h Preliminary Scheme Exercise 1 Tuesday 31/8, Stepwise polymerization 1.1, 1.6, 1.10 Exercise 2 Thursday 6/9, 8-10 Chain polymerization 2.1, 2.4, 2.5, 2.8 Exercise 3 Friday 9/9, Copolymerization 5.1, 5.3, 5.5, 5.9 Exercise 4 Monday 12/9, Emulsion, ion and coordination polymerization 3.1, 3.3, 4.1

3 Exercise 5 Monday 3/10, 8-10 Polymers in solution and molecular weight characterization 6.1, 6.5, 6.8, 7.1, 7.5, 7.10 Exercise 6 Monday 10/10, 8-10 Exam problems from previous years The home assignments The correct solutions of three home assignments should be handed in. The home assignments must be approved before you can obtain grades on the course. The home assignments should be prepared individually, and solutions should be handed in for corrections and approval. You hand in the assignments in mail boxes outside our department library marked Thanh Huong Pham, Hai-Son Dang, and Joel Olsson, respectively, and you receive the assignments after correction in the box marked Laborationsrapporter UT. Errors should be corrected and modified solutions should be handed in again. Approved assignments will be handed out before the exam. Home assignment 1 is to be handed in no later than the 20th of September to Thanh Huong Pham (Polymer & Materials Chemistry) Home assignment 2 should be handed in no later than the 30th of September to Joel Olsson (Polymer & Materials Chemistry) Home assignment 3 is to be handed in no later than the 6th of October to Hai-Son Dang (Polymer & Materials Chemistry) Thanh Huong Pham thanh_huong.pham@chem.lu.se Hai-Son Dang hai-son.dang@chem.lu.se Patric Jannasch patric.jannasch@chem.lu.se Joel Olsson joel.olsson@chem.lu.se

4 Home Assignment 1 Engineer Al Kyde is preparing two polymers, a polyester and a polyacrylamide. The polyester should have the molecular weight g/mol, and Al wants to prepare 900 g of the polyacrylamide. To prepare the polyester he is using the receipt: Phthalic acid Maleic acid Diethylene glycol Pentaerythritol 355 g 245 g 370 g 80 g The reaction was carried out in toluene with a mineral acid as catalyst. Al measures the acidity after 1 h reaction, and finds that 21.0 % of the acid groups remain unreacted. To prepare the polyacrylamide Al has the following information: The reaction is carried out at 25 C with 100 g/l acylamide in methanol and with 0.1 M isobutyryl peroxide as initiator. The half-time for isobutyryl peroxide is 9.0 h, and for acrylamide k p 2 /k t = 22 l/(mol s) at 25 C. Termination occurs only by combination. f = 0.3. Al is using a 10 l reactor to polymerize the acrylamide. Draw the reactions that occurs in the two cases How long reaction time is required for the two polymerizations? How long is the time margin between the finished product and gelation in the polyester reaction? What is the molecular weight of the polyacrylamide? Approximations should be clearly noted and motivated. Guidance: dx x a bx 1 a bx ln a x

5 Home Assignment 2 Problem A. Calculate the polymer compositions, F 1, obtained at copolymerizations at low conversions for the monomer pairs below. Assume that the initial monomer mixture is equimolar. Monomer 1 Monomer 2 r 1 r 2 Ethylene Vinyl acetate Methyl acrylate Methyl methacrylate Methyl methacrylate Styrene Maleic anhydride cis-stilbene Styrene Vinyl chloride Problem B. Draw the polymer composition, F 1, versus the monomer composition, f 1, for the monomer pairs above. Put f 1 = 0, 0.1, 0.2.., 1.0, and calculate the corresponding F 1 - values by using the copolymerization equation. Draw the diagonal, that is when F 1 = f 1, in the diagram. a. Which monomer pairs give ideal copolymers, and which give alternating? b. When the copolymerization curve coincides with the diagonal we have azeotropic conditions. What does this mean? c. At which monomer compositions do we have azeotropic conditions? Problem C. In Appendix 1 of the handouts on copolymerization (Swedish version) are the results listed in tables from a number of experiments where the polymer compositions, F 1, have been determined after copolymerization at known monomer compositions, f 1. The copolymerizations have been driven to low conversions (<5%). Choose one of the experiments and determine the copolymerization parameters by: a. The slope-method b. The Finemann-Ross method

6 Home Assignment 3 Problem A. You shall determine the chain transfer constant for carbon tetrachloride during thermal bulk polymerization of styrene. Three polymerizations have been carried out with different amounts of carbon tetrachloride: Polymerization nr [CCl 4 ] (mol/l) The polymerizations were terminated at 5 % conversion. Viscometry was used to determine the molecular weights obtained in the polymerizations. Concentrations and the obtained flow times are shown in the tables below. Polymerization nr 1 Polymer conc., (g/ml) time (s) Polymerization nr 2 Polymer conc., (g/ml) time (s) Polymerization nr 3 Polymer conc., (g/ml) time (s) The flow time for the pure solvent was s. For polystyrene, K= ml/g, and a=0.70 in the solvent used. You can assume that M v = M n. Determine the chain transfer constant and estimate the molecular weight for polystyrene polymerized without the presence of chain transfer agent. If you want to prepare polystyrene which has a molecular weight of g/mol at the very initial stages of the polymerization, how many grams of carbon tetrachloride should you add if you start with 10 kg of monomer? The density for styrene is g/ml.

7 Problem B. Given that the repeating unit in polystyrene is 104 and that the distance between the carboncarbon bonds in the main chain is 1.54 Å calculate the following: a. The mean-square end-to-end distance for a polystyrene molecule with the molecular weight 10 6 by assuming that the molecule behaves like a freely rotating, freely joined volumeless chain. Further assume that each link is equivalent with one carbon atom in the main chain. b. The unperturbed root-mean-square end-to-end distance, <r 2 > 0 1/2, given that the relationship between the limiting viscosity,[], and the molecular weight of polystyrene in a -solvent is given by: []= M 0.5 where [] is in dl/g and the Flory-Fox constant () is dl/(g cm 3 ). c. The radius of gyration for polystyrene with the average molecular weight 10 6 under - conditions.

Quiz 5 Introduction to Polymers

100506 Quiz 5 Introduction to Polymers 1) Polyurethane in the video shown in class is formed from two liquids that are mixed. After mixing the solution foams and expands fairly rapidly forming a solid