The aim of this project was to design novel polymerisable UV absorbers which successfully protect PET from UV degradation for a longer duration of time compared to non-polymerisable UV stabilising additives. The polymerisable UV stabilisers for PET were synthesised using cyanuric chloride as a synthetic starting point. A number of synthetic monomers were prepared based upon one of the most effective UV stabilising additives employed currently in the polymer industry, Tinuvin 1577. UV absorbing monomers (UVAMs) with chromophores different to that of Tinuvin 1577 were synthesised, and many were found to have higher molar absorptivity than Tinuvin 1577. The novel UVAMs were copolymerised with bis(hydroxyethyl)isophthalate to yield copolymers of poly(ethylene isophthalate) (PEI). In certain cases, more than one UVAM was copolymerised into the same PEI chain to obtain a broader UV coverage and to distribute the UVAMs in the middle and end of the polymer chains. Copolymers were purified to remove any unreacted monomers and characterised by UV-VIS spectrophotometry, 1H NMR spectroscopy and DSC to demonstrate and quantify successful incorporation of the UVAMs into the polymers. PET copolymer films containing 3-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)-3- hydroxyphenoxy]-1,2-propanediol (32), 6,6'-(6-phenyl-1,3,5-triazine-2,4-diyl)bis(3-(2- hydroxyethoxy)phenol) (37) and both 32 and 37 were weathered alongside a PET control and PET containing Tinuvin 1577 1.10. The films were exposed for 1082 hrs in a QUV weatherometer and analysed periodically using FT-IR spectroscopy and GPC. The results showed that the films containing UVAMs outperformed the films containing Tinuvin 1577, offering greater protection to the polymer films against crosslinking and chain scissions.