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ISSUES TO ADDRESS...

• How do general structural & chemical characteristics of different types of polymer molecules affect mechanical properties?

• What are some common polymers & how do they differ?

Chapter 14: Polymer Structures – Polymers I: Concept & Synthesis of Polymers

Class 17 – Chapter 14: Polymers I - Structure & Concept - Topic #6.1

• How are polymers synthesized?

• How can polymers be categorized?

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What is a Polymer?

Poly mer Many Units

C C C C C C H H H H H H

H H H H H H

Polyethylene (PE) Cl Cl Cl

C C C C C C H H H

H H H H H H

Poly(vinyl chloride) (PVC) H H

H H H H

Polypropylene (PP)

C C C C C C CH3

H H

CH3 CH3 H

repeat unit

repeat unit

repeat unit

What is the Geometry of a Polymer Chain?

C-­‐C  rota(ons  along  the  chain  give  the  polymer    molecule  a  loosely  coiled  string-­‐like  shape    

What are Important Polymer Concepts & Terminology?

Polymer MW Effects on Properties – Melting Point MW  of  Chain  =  n(DP)  *  MW  Monomer  

                                                                                     =  n(DP)/2  

Why does the Tm increase with more C atoms in chain?

What are the similarities and differences of candles and plastic milk containers?

Candle   Container  

n  (DP)   11   10,000  

MW  (g/mol)   28(11)  =  1400  g/mol   28(10000)  =  28000  g/mol  

Extended  Chain  Length    

15  nm   3100  nm  

Tm  (degrees  C)  

6 6

Free Radical (Addition) Polymerization –  Initiation

–  Propagation

–  Termination

C

H

H

O O C

H

H

C

H

H

O2 R= 2

– Free Radical Initiator Benzoyl Peroxide

Thermoplastic Addition Polymers - Vinyls

Semicrystalline Semicrystalline Amorphous Amorphous