Chap._100015 - Head-to-head linkage is usually the source...

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B B B B B B -A-A-B-A-B-B-A-B-A-A-A-B- Random copolymer -A-B-A-B-A-B-A-B-A-B-A-B- Alternating copolymer -A-A-A-A-A-A-B-B-B-B-B-B- Block copolymer -A-A-A-A-A-A-A-A-A-A-A-A- Graft copolymer n (A) monomers + m (B) monomers *Structure Unit Orientation (Regio-selectivity) A further possible variable in polymer structure arises from the two potential orientations as it adds to the proceeding unit. poly(vinyl chloride) PVC Cl Cl Cl Cl Cl Cl -CH 2 -CH-CH 2 -CH- head-to-tail linkage -CH 2 -CH-CH-CH 2 - head-to-head linkage --CH-CH 2 -CH 2 -CH- tail-to-tail linkage vinyl chloride Cl CH 2 =CH The orientation of monomer addition is influenced by propogating site (originated by catalyst), monomer (steric and electronic factors) and reaction temperature.
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Unformatted text preview: Head-to-head linkage is usually the source of instability (thermal, UV, etc.). * Polymer Tacticity (Stero-selectivity) A further possible variable in polymer structure arises from the orientation of side groups along the polymer chain. Isotactic polymer: repetition of the same configuration of repeating units Syndiotactic polymer: alternation of configuration Atactic polymer: a random arrangement n all head-to-tail linkage but there are three tacticities i-PP, s-PP and a-PP Polypropylene (PP) Propylene (1-propene) CH 3 CH 3 CH 3 CH 3 CH 3 CH 3 CH 2 =CH -CH 2-CH-CH 2-CH-CH 2-CH-CH 2-CH-CH 2-CH-...
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This note was uploaded on 10/16/2010 for the course MATSE 441 taught by Professor Chung,tze-chiang during the Fall '10 term at Penn State.

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