The Department of Physics, Chemistry and Biology

LinköpingUniversity

Examination of TFYY42

Polymer Physics

Thursday 31 May 2007 1400-1800

Aid only: Physics handbook, mathematical formulas book, calculator and ruler.

There is no particular order with respect to theme or difficulty.

Name acronym and number on all papers! Explaining is important: even an erroneous answer might render credits if it is readable.

Describe the difference between configuration and conformation. (2p)

(a) Prove that the weight-average molar mass is never smaller than the number-molar lass and therefore the polydispersity index is never less than unity:

(b)Consider a blend obtained by mixing 1g of a polymer with molar mass MA=1×105gmol-1 and 2g of the same type of polymer with molar mass MB=2×105gmol-1.

(ii)Calculate the number-average molar mass Mn of this blend.

(iii)What is the weight-average molar mass Mw of this blend.

(iv)What is the polydispersity index of this blend?

(4p)

List the factors, which influence the glass transition temperature (Tg) and describe in which way they effect Tg.

(2p)

All polymers dissolved in theta solvents,the end-to-end distance of polymer chains adapt to the following equation:

For polyethylene describe under which conditions C=1, C≈2 and C>2.

(3p)

5. In Flory-Huggins equation, which term presents contribution of entropy and which term presents contribution of enthalpy? Describe the necessary conditions for miscibility of polymer. Why most polymers are immiscible in solvents.

Describe what are spinodal point and binodal point. Find out and mark S and B points on the curves if they have these points in the figure below

(4p)

What is viscoelasticity? Name following liquid-crystals.

(2p)

How can you distinct a crystalline polymer from an amorphous polymer? What are geometrical and physical requirements for crystalline polymers? Draw schematic curves to show cooling a liquid to form a crystalline or amorphous structure. (3p)

You have a monodisperse polymer sample with chains all of length N monomers, in a theta solvent. By an act of grace, the chains are all split into two equal parts, N/2 long (N>1). Predict the change of viscosity and osmotic pressure in the solution. What would happen with these parameters if the solvent was a good solvent for the polymer?? (3p)

Thin polymer films are essential to polymer electronics. The formation of thin films (<1µm thick) is typically by spin coating from solvents. Describe the formation of micro and nanostructure in a film prepared by spin-coating a blend of two fluorescent electronic polymers! How would these structures be imaged?

(4p)

A point mass with weight M is suspended in a rubber band, which is elongated by 25% compared to the non loaded rubber band. The rubber is heated from room temperature to 125 C. What is the position of the mass? (3p)