Dr. Mark Liff
M.S. in Materials
POLYMER AND FIBER PHYSICS
office: Search Hall, R#320, ph. 951-2879
This course will introduce you to the physical properties
of polymers and the investigation of the structure-property relationships in polymers by
physical methods. The focus will be on the mechanical, thermodynamical and
dielectric behavior of polymers. The
statistical description of an isolated chain will be followed by the theories of
rubber elasticity and viscoelasticity. The theory of the glass-rubber transition and the
behavior of glasses, rubbers and melts will be discussed. Molecular motion and its
manifestation in the mechanical, dielectric and NMR experiments constitute an important
part of this class. The molecular structure of textile fibers, including natural protein
fibers (silk, wool) will be discussed as well.
Listing of Topics.
- 1. Types of polymer structure: linear, branched,
networked. Most common polymers and their end-use properties. Introductory ideas about
- 2. Rotational isomerism in small molecules. Ethane,
n-butane. Trans and gauche positions. The energy dependence on rotational angle.
Conformational state of a polymeric molecule. Number of conformations in a polymer.
- 3. Brownian motion in liquids, gases and solids.
Correlation time and frequency. Specifics of molecular motion in polymers. Local,
segmental and large scale motion in polymers and orders of the correlation time.
Average end-to-end distance for a flexible chain (average over time, average over
ensemble) Substitution of a real chain by a model. Random walk, random flight. Freely
jointed chain. Average end-to-end distance for a freely jointed chain. Comparison to a
real chain. The idea of a statistic segment. The probability of finding two ends at a
given distance. Elasticity. Entropic nature of rubber elasticity.
- 6. Ordered chain conformation. Polyethyleneterephthalate,
nylon. Bulky substituents, polytetrafluoroethelene. Stereoregularity and microtacticity.
Helical structures generated by succession of trans and gauche conformations.
- 7. Glass transition. Free volume theory. The equation of
William-Landels -Ferry. Incremental method for the determination of Tg. Dependence of Tg
on molecular weight.
- 8. Crystal structures. Lamella, micelle, fibril,
spherulites. Crystallization from solution and from melt.. The changes in properties on
crystallization. Dependence of melting on distribution of molecular weight. Dependence on
branching. A mesomorphic state.
- 9. Fibers. Orientation. The basic scheme of fiber
spinning. Typical force-length diagrams. Young modulus. Breaking tenacity. Length
-temperature relationship. Shrinkage (contractility). Protein fibers. Typical structure of
proteins (alpha-helix, beta- sheet). Silk. Wool.
- 10. Molecular weight, M
(number average, weight average). Light scattering and M determination. Raleigh ratio,
its dependence on M and directional angle. Additivity of scattering from a solute and a
solvent. The schematic of light scattering instrumentation. The asymmetry of light
scattering when a wavelength is comparable to molecular dimensions. Zimm's double
extrapolation for obtaining M.
- 11. Centrifugation. The principle of M determination by
ultracentrifugation. Method of sedimentation velocity. The Svedberg factor and the
diffusion factor. Svedberg equation. Sedimentation equilibrium.
- 12. Molecular weight and viscosity. Viscosity and Stokes
law. Capillary viscometry and time of flow. Relative, specific, reduced and characteristic
viscosity. Mark-Howink equation for dependence of viscosity on M.
Mechanical properties of polymers. Dependence of correlation time and viscosity on
temperature. Activation energy barrier. Temperature dependence of modulus: correlation
with glass and melt transitions. Dependence of stress on time upon application and removal
of a constant force at different states: glass, rubber, melt, viscoelastic polymer.
Stress-strain diagrams: initial and secant modulus, yield point, breaking tenacity.
Instruments with a constant rate of elongation and loading: Instron, chainomatic method,
inclined plane method. Work of rupture and its measurement. Elastic recovery
for crystals, plastics, rubber networks, melts. Time effects during recovery.
- 14. Models of viscoelastic behavior. Springs and pistons.
Parallel and in series connections. Examination of relaxation and creep on Kelvin and
Maxwell models. Dynamic testing.
Diagram of force versus elongation for a spring and a piston. Energy losses. Quantities
E', E'', A, tan d and their dependence on frequency of testing and molecular
motion. Shear modulus. Poisson ratio. Four- parameters models. Accounting for distibutions of relaxation and retardation times.
- 15. Thermal analysis. Principles and applications.
Differential thermal analysis. Differential scanning calorimetry. Thermomechanical
analysis. Thermogravimetric analysis. Dynamic mechanical thermal analysis. Dielectric
- 16. Electrical properties. Measurements of conductivity,
influence of moisture. Conductivity of fibers (volume or surface, ionic or electronic?).
Static charges in fibers. Triboelectricity. Piezoelectricity.
- 17. Application of Nuclear Magnetic Resonance to some
problems of Polymer Science: molecular weight determination, microtacticity, molecular
Texts for FB12:
Painter, P & Coleman, M. Fundamentals of Polymer
Science, 1997 (available in the bookstore).
Eisele, U., Introduction to Polymer Physics, Springer
Verlag, Berlin, 1990.
Mark, J., E., et al. Physical Properties of Polymers,
ACS, Washington, DC, 1993
Cowie, J. M. G. Polymers. Chapman and Hall, any edition.
Tests (min 2 and max 4, as needed) ............. 50 %
final.......................................................... 40 %
Review of 2 articles
......................................................... 10 %.
Time for the tests will be announced one week in advance.
If you are 1-2 points short of A, B, C, you will be
graded A-, B- or C-, correspondingly. If you are in B or C limits and 3-4 points short of
getting a higher grade, you will be graded B+ and C+, accordingly.
Special bonus for a successful final exam.
If you get A or B for your final all your other grades
that are lower than the grade for the final will be disregarded and substituted by that
higher grade. To qualify for this bonus your reviews should be turned in on time and
graded no less than C+ and you must take all in-class tests.
Make-ups. The percentage of the
missed test automatically goes into the final. The final exam is mandatory. There will be
no individualized make-ups.
Attempts to obtain information from the sources other than those specified by the
instructor during the tests and the final will not be tolerated.
PowerPoint presentation on the NMR of Wool