Impact of Carbonyl Group Incorporation in Semicrystalline High-Density Polyethylene

Ketone-functionalization of polyethylene via copolymerization with carbon monoxide offers a promising route to introducing reactive carbonyl moieties while preserving the advantageous bulk properties of high-density polyethylene (HDPE). Here, we systematically investigate the influence of low-level (0.6-1.6 mol %) keto incorporation on the thermal properties, semicrystalline morphology, crystallization, and chain dynamics of HDPE. Differential scanning calorimetry and small-angle X-ray scattering reveal only minor reductions in melting temperature and lamellar thickness. Complementarily, ¹H NMR FID measurements reveal that KetoPE samples exhibit crystallinity-temperature profiles comparable to HDPE, indicating that the semicrystalline morphology is mainly preserved upon keto incorporation up to a few percent. Importantly, ¹³C T ₁ relaxation quantitatively confirms that intracrystalline chain diffusion coefficients are essentially unchanged. Notably, ¹H spin-diffusion NMR confirms that presumably the isolated carbonyl moieties predominantly reside in the interphase. Thus, low-level ketone incorporation imparts additional reactivity or adhesion potential without compromising HDPE's mechanical or thermal integrity.