Raman spectroscopy has been used to reveal the microscopic structural changes of low-density polyethylene under ultraviolet irradiation. The fraction of non-crystalline consecutive trans chains (the molecular chains in the trans conformation separate from the orthorhombic crystalline phase) drastically decreases at ∼600 h, together with a decrement in the molecular weight and an increment in the crystallinity owing to chemicrystallization. This suggests that short trans chains are prolonged to form consecutive trans chains before chemicrystallization. Moreover, gradual increases of the stretching and compression stresses are observed on the trans and amorphous chains, respectively. These conformational changes are detected by Raman spectroscopy even in the early stage of photodegradation. Chemicrystallization at ∼600 h is accompanied by structural changes, such as shortening of the interchain distance of the lamellar crystals and thinning of the amorphous layer, which induce formation of surface cracks on the macroscopic specimen.

拉曼光谱法已被用于揭示紫外线照射下低密度聚乙烯的微观结构变化。非晶态连续反式链的部分（反式构象的分子链与正交晶体相分离）在〜600 h时急剧减少，同时由于化学结晶，分子量降低，结晶度增加。这表明短的反式链在化学结晶化之前被延长以形成连续的反式链。此外，分别在反式和无定形链上观察到拉伸应力和压缩应力的逐渐增加。这些构象变化即使在光降解的早期也可以通过拉曼光谱法检测到。