MSE-BioE+C118+_10+L_5+-+7+W

MSE-BioE+C118+_10+L_5+-+7+W - MSE/BioE 118 Lectures #4...

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MSE/BioE 118 Materials Science and Engineering Polymer Science Continued Temenoff and Mikos Chapters 3.6, 4.2.3 Outline 9. Transitions in Polymers 10. Mechanical and Viscoelastic Properties of Polymers Design example: biodegradable stent deployment 11. Models for Linear Viscoelasticity www.ciwmb.ca.gov 9. Transitions in Polymers Molecular motions in polymers temperature dependent T g = glass transition temperature Other transitions 1. Translational motion of entire molecules, flow 2. Flexing and uncoiling of chains 3. Motions along chains 4. Vibrations about equilibrium positions @ T g 1 and 2 “frozen” out, only 3 and 4 active How do you measure T g ? Δ H = kT
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Glass-Rubber Transition Behavior Glass Transition Temperature (T g ) Glass State Strong Stiff Brittle (less than < 3% elongation) Restricted molecular motions: vibrations, rotations Rubber State Elastic Leathery Pliable: large elongation, > 200% Long-range coordinated molecular motions 6 Temenoff & Mikos 3.6
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MSE-BioE+C118+_10+L_5+-+7+W - MSE/BioE 118 Lectures #4...

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