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Question 1 A pair of monomers M1 and M2 undergoing radical chain copolymerization were found to have reactivity ratios r1 = 0.1 and r2 = 10.0. What is the composition of the initial copolymer that is formed when the monomer feed contains (a) an equimolar amount of M1 and M2 and (b) 2 moles of M1 per mole of M2? Show how you arrived at your answers. Question 2 A sample of polystyrene was synthesized by reversible deactivation radical polymerization (RDRP) of 5 moles of styrene initiated with 0.05 moles of 1 phenylethyl bromide in the presence of CuBr and a coordinating amine ligand (ATRP method). Analysis of the polymer by size exclusion chromatography (SEC), indicated a number average molecular weight of 7,150 g/mole at 72% conversion. (a) Calculate the theoretical molecular weight for the sample and compare it with the experimentally observed value obtained by SEC analysis. (b) Calculate the theoretical molecular weight that is attained when the polymerization is carried-out to full conversion of monomer under these conditions. (c) Predict the molecular weight of the block copolymer that is obtained when 5 moles of 4-tert-butylstyrene is added to the reaction mixture of part (b) above (macroinitiator) after all the styrene has been consumed. Assume complete conversion of 4-tert-butylstyrene. (d) Draw the chemical structures of the polystyrene macroinitiator and the poly(styrene-block-4-tert-butylstyrene) block copolymer clearly showing the repeating units, end groups and degrees of polymerization (as numerical values of repeating unit subscripts "n"). Question 3 Estimate the extent of reaction at which gelation occurs for the mixture of monomers listed below. Show how you arrived at your answers and comment on the accuracy of the method or methods used in your calculation: (a) A stoichiometric mixture of adipic acid and pentaerythritrol. (b) A mixture of adipic acid, diethylene glycol and trimethylolpropane in mole proportions 10/4/4. (c) A mixture of 6 moles adipic acid, 3 moles diethylene glycol, 2 moles trimethylolpropane and 1 mole pentaerythritol. Structures of the monomers are as follows: COCH HOOC Adipic acid (A2 monomer) OH OH o HO OH OH HO OH OH OH Diethylene glycol Trimethylolpropane Pentaerythritol (B2 monomer) (B3 monomer) (B4 monomer) Question 4. A 9/1 mole blend of butyl acrylate (BA) and glycidyl methacrylate (GMA) are copolymerized to full conversion in a metal-catalyzed RDRP at a monomer/initiator ratio of 100/1. The resulting epoxy-functionalized copolymer is a viscous liquid that is fully soluble in organic solvents. However, when mixed with 0.25 moles diaminodiphenylmethane (DPM) and heated, it forms a solid, insoluble crosslinked polymer network. (a) Draw a structure representing the repeat unit of the copolymer that is formed in the RDRP reaction. Indicate the degrees of polymerization associated with each unit, assuming a fully random copolymer is obtained. (b) Describe the principal crosslinking reaction that occurs when the copolymer is blended with DPM and heated. (c) Draw an idealized structure of the crosslinked network, showing at least one complete primary crosslinked unit. (d) Describe additional reactions that can occur during the primary crosslinking and comment on how these reactions affect the crosslink density of the polymer network. H2N, NH2 'o o o 20 Butyl acrylate Glyctdyl methacrylate 4,4'-dlaminodiphenyimethane(DPM)

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1.
Copolymer composition equation for chain reaction is given by the equation,
d[M1]/d[M2] = [M1](r1[M1]+[M2])/[M2]([M1]+r2[M2]
d[M1]/d[M2] is the molar ratio of the two monomers and is related to the concentrations of the feed [M1] and [M2] and monomer reactivity ratio parameters i.e. r1 and r2.
Here, r1 is lesser than unity means that m1* preferentially adds M2. Whereas r2 is greater than unity means M2* preferentially adds to M2.
When M1 and M2 undergo radical chain copolymerization with r1 = 0.1 and r2 = 10.0, then r1 x r2 = 1. This is known as ideal polymerization.
d[M1]/d[M2] = [M1]r1/[M2]...

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