1. Based on sources
2. Based on structures -
3. Based on modes of polymerization: (Composition/Structure)

Addition: Two or more molecules combine to form one large molecule. $$\mathrm{CH}_2=\mathrm{CH}_2+\mathrm{Cl}_2 \rightarrow \mathrm{CH}_2 \mathrm{Cl}-\mathrm{CH}_2 \mathrm{Cl}$$

• $\left.n \mathrm{CH}_2=\mathrm{CH}-\mathrm{CH}=\mathrm{CH}_2 \rightarrow [-\mathrm{CH}_2-\mathrm{CH}=\mathrm{CH}-\mathrm{CH}_2 -\right]_n$

(1,3-Butadiene)

• $$\begin{aligned} & n \quad \mathrm{CH}_2=\mathrm{CHCl} \ \end{aligned}\xrightarrow{Polymerization} [-\mathrm{CH}_2-\mathrm{CHCl-}]_n$$poly(vinyl chloride) PVC

$\mathrm{Na}$

• Homo polymers

Condensation reactions:

• Two or more molecules react to produce one molecule along with production of small molecule like water, methanol $$\begin{aligned} & \mathrm{CH_3} \mathrm{COOH}+\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{OH} \ & \longrightarrow \mathrm{CH}_3-\mathrm{COOCH}_2 \mathrm{CH}_3+\mathrm{H}_2 \mathrm{O} \ & \text { Ethylacetate } \ & \end{aligned}$$

Nylon 6,6.

• $nH_2N-(CH_2)_6-NH_2 (hexamethylene \hspace{1mm} diamine)+nHOOC-(CH_2)_4-COOH (adipic \hspace{1mm} acid) \rightarrow [-HN-(CH_2)_6-NH-CO-(CH_2)_4-CO-]_n+(2n-1)H_2O$ (Polyamide hexamethylene adipimide) Nylon 6,6

• $nH_2N-(CH_2)_5-COOH \rightarrow [-HN-(CH_2)_5-CO-]_n+(2n-1)H_2O$ Nylon 6

PET

• $nHOOC-C_6H_4-COOH+nHO-CH_2-CH_2-OH \rightarrow [-OC-C_6H_4-COO-CH_2-CH_2-O-]_n(Poly \hspace{1mm} ethylene \hspace{1mm} teraphthalats) +(2n-1)H_2O (HOMO)$
• $nHOOC-C_6H_4-COOH+ \frac{n}{2} OH-CH_2-CH_2-OH+ \frac{n}{2} OH-CH_2-CH_2-CH_2-CH_2-OH$ $\rightarrow$ Poly (fethylene-co-butylene terephthalate) (Copolymer)

4. Based on mechanism of polymerization

$CH_2=CH-C_6H_5 \rightarrow [-CH_2-CH-]_n-C_6H_5-$

• Radical cation anion
• Initiation

$CH_2=CH-R+ I^.$ $\rightarrow$ $I-CH_2-C^* H-R$ + $CH_2=CH-R$ $\rightarrow$ $I-CH_2-CH(R)-CH_2-C^{*}H-R$

• Propagation

• Polymers are produced by addition of monomers at the end of growing chain $\rightarrow$ Chain-growth polymerization, Chain-growth polymers

• Termination

• 4-Based on mechanism of polymerization

• Radical cation anion

• Propagation

$$I^.$$

• Thermal initiators: covalent bonds which can be homolytically cleaved into the radicals by heating

• $\phi-CO-O-O-CO-\phi(benzoyl \hspace{1mm} peroxide) \xrightarrow {\Delta} 2\phi-CO-O^. \rightarrow 2\phi^.+2CO_2$

• t-butyle peroxide $(CH_3)_3-C-O-O-C-(CH_3)_3$

Acetyl peroxide

$CH_3-CH_2-CO-O-O-CH_2-CH_3$

• 2,2’- Azobisisobutyronitrile (AIBN)

$(CH_3)_2CN^-C-N=N-C-(CH_3)_2CN^-$

$X \xrightarrow {\Delta} 2I^. \xrightarrow {CH_2=CH-R} I-CH_2-C^.H-R$

Propagation

• Termination

$-CH_2-C^.H_2-$

$-CH_2-CH_2-$

$-CH_2-CH_2-CH_2-CH_2-$ coupling

$-CH=CH_2$

$-CH_2-CH_3$ disproportionation

• Chain - growth
• Initiation → propagation → Termination

Polyester formation

• $nHO-R-OH (monomer \hspace{1mm} A)+ nHOOC-R^{’}-COOH (monomer \hspace{1mm} B) \rightarrow -CO-O-+H_2O \rightarrow OH-R-O-CO-R^{’}-COOH$ (dimer)

• Dimer $\hspace{1mm} + \hspace{1mm}$ monomer $\rightarrow$ trimer

• Dimer $\hspace{1mm} + \hspace{1mm}$ Dimer $\rightarrow$ tetramer

• Generally (not always)
• Addition $\leftrightarrow$ chain-growth
• Condensation $\leftrightarrow$ step-growth
• Exception (one example)
• $HO-R-OH (diol) + OCN^–R^{’}-NCO (diisocyanate) \rightarrow [-O-R-O-CO-N-R^{’}-NH-CO-] (polyurethane)$
• Addition Step-growth

• Stress: Force/area = F/A
• Strain: change in diamension/original length = $\Delta$ L/L

• $\frac{\text { Stress }}{\text { strain }}=$ Modulus (Resistance to deformation) Elastomers high elongation $\geqslant 5-10$ times $\geqslant$ 500-1000% Reversine Modulus is low