Match the Polymer with the most suitable Monomer combinations from which it is synthesized.
\[
\begin{array}{|c|c|}
\hline
\text{Polymer} & \text{Monomer combinations} \\
\hline
P: \text{Polyurethane} & 1: \text{Maleic acid and propylene glycol} \\
Q: \text{Epoxy} & 2: \text{Pyromellitic anhydride and p,p'-diamino diphenyl ether} \\
R: \text{Polyimide} & 3: \text{Epichlorohydrin and bisphenol A} \\
S: \text{Polyester} & 4: \text{Hexamethylene diisocyanate and tetramethylene glycol} \\
\hline
\end{array}
\]