Chapter 2. Chain Structure and Configuration

1. Chapter 2. Chain Structure and Configuration

2. Polymer chains have three basic properties: • The molecular weight and molecular distribution. • The conformation of the chains in space. • The configuration of the chain. Coil chain conformation

3. 2.1 Examples of configurations and conformations 2.1.1 Head-to-head and head-to-tail configurations head-to-tail head-to-head Thermodynamically and spatially preferred structure is usually the head-to-tail configuration. The H-to-H and H-to-T configurations cannot be interchanged without breaking primary chemical bonds.

4. 2.1.2 Trans-Gauche Conformations The trans-gauche conformations of polymer chain can be interchanged by simple rotation about the single bond linking the moieties.

5. 2.2 Theory and instruments 2.1.2 Chemical methods of determining microstructure

7. 2.3 Stereochemistry of repeating units 2.3.1 Chiral centers * Chemically identical but they rotated plane-polarized light in opposite directions.

8. 2.3.2 Tacticity in polymers Polymerization of monosubstituted ethylene Pseudochiral center

9. isotactic syndiotactic atactic

11. Stereo-isomers

13. 2.4 repeating unit isomericsm 2.4.1 Optical isomerism

14. 2.4.2 Geometric isomerism The cis-trans isomerism arises because rotation about double bond is impossible without disrupting the structure.

15. 2.4.3 Substitutional isomerism Synthesis of diene type polymers 1,2 1,4 3,4 addition polymerization isoprene

16. 2.4.4 Infrared and Raman spectroscopic characterization C-H bending 823 cm-1 C-O stretching 1164 & 1231 cm-1 C=O stretching 1506 cm-1 Skeletal ring vibration 1776 cm-1

18. 2.5 Common types of copolymers

19. Copolymers Terpolymers

20. Polymer blend Graft copolymer IPN Block copolymer Semi-IPN Cross-linked

22. Nanoscale ‘microphase’ segregation: cN > (cN)ODT with (cN)ODT = f(f) Melt state

23. ‘Solution’ state: Swollen micelles and dissolved single-chains Blends?

24. Crystalline state

25. Block Copolymer (microphase separation) volume fraction < 0.20 0.20 ~ 0.35 > 0.35

26. Transition between mesomorphic phases

27. Block Copolymer phase diagram disorder

29. Representative phase diagram of diblock copolymers(Khandpur et al., Macromolecules1995, 28, 8796)

30. 3-D TEM micrographs for PS280-PLLA307 (fPLLA= 0.37) solution-cast samples sectioned along different planes. As shown, the xy plane is the basal plane normal to helical axes and the yz and zx planes are planes parallel to helical axes

32. ‘Knitting’ pattern

33. 2.8 Conformational states in polymers Arrhenius type: Exp(-Eact/kT) g- g+ t

34. 2.9 Analysis of polymers during mechanical strain Far from the neck region In the neck region

35. 2.10 Photophysics of polymers quench A + hu = A* A* + B = A + B* 2.10.2 Excimmer formation A* + A = (AA)* (AA)* = 2A + huE

36. 2.10.3 Experimental Studies 2.10.3.1 Microstructure of polystyrene

39. Infrared