Polymer Chemistry

​Polymer Materials: Structure and Fundamentals

​1. Definition & Key Concepts

​Polymers are ​macromolecules composed of repeating structural units (monomers) linked by ​covalent bonds.​Molecular Weight: Typically ranges from ​10⁴ to 10⁶ g/mol, distinguishing them from small-molecule compounds.​Example:​Polyvinyl Chloride (PVC) is formed by repeating ​**–CH₂–CHCl–** units derived from ​vinyl chloride (CH₂=CHCl) monomers.

​2. Basic Terminology

Term	Definition	Example
​Monomer	Small molecule that polymerizes to form a polymer.	Ethylene (C₂H₄) → Polyethylene (PE).
​Structural Unit (Repeat Unit)	The smallest repeating segment in a polymer chain.	​**–CH₂–CHCl–** in PVC.
​Degree of Polymerization (DP)	Number of repeat units in a polymer chain.	PVC with DP = 1000 has 1000 ​**–CH₂–CHCl–** units.

​3. Classification of Polymers

​By Origin​Natural Polymers: Cellulose, proteins, DNA.​Synthetic Polymers: PVC, polyethylene (PE), nylon.​By Structure​Linear Polymers: Single-chain structure (e.g., HDPE).​Branched Polymers: Side chains attached (e.g., LDPE).​Cross-linked Polymers: 3D network (e.g., vulcanized rubber).​By Polymerization Mechanism​Addition Polymers (Chain-growth): PE, PP, PVC.​Condensation Polymers (Step-growth): Nylon, PET.

​4. Polymer Synthesis Methods

Method	Process	Example
​Addition Polymerization	Monomers add sequentially without byproducts.	​PVC from vinyl chloride.
​Condensation Polymerization	Monomers react with byproduct release (e.g., H₂O).	​Nylon-6,6 from adipic acid + hexamethylenediamine.

​5. Properties & Applications

Property	Impact	Application Example
​High Strength-to-Weight Ratio	Light yet durable.	​Packaging films, automotive parts.
​Chemical Resistance	Inert to acids, solvents.	​Chemical storage tanks (PP, PTFE).
​Flexibility/Thermoplasticity	Moldable when heated.	​PVC pipes, PET bottles.
​Insulation	Non-conductive.	​Wire coatings, circuit boards.

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