PLLA forms a charge-transfer (CT) complex with iodine in trichloromethane solution with Keq = 24.8 ± 1.8 M^-1, much higher than the Keq = 0.75 M^-1 measured with the model compound ethyl lactate-iodine in CHCl₃. The higher equilibrium constant of the PLLA-I₂ complex suggests a special polymer-iodine interaction which was confirmed by optical rotatory dispersion (ORD) measurements, taking advantage of the fact that PLLA is an optically active polymer. In fact, ORD measurement shows an induced Cotton effect at 500 nm giving further support to the model of iodine accommodated inside the helical coils of PLLA chains in solution. The PLLA-I₂ complex was found very stable if stored in the dark and in the cold (i.e. +10 °C). The PLLA-I₂ complex shows both the growth of the CT bands in the electronic spectrum and the induced Cotton effect in the ORD spectrum after prolonged storage. However, the PLLA-I₂ complex is sensitive to visible light and it dissociates upon irradiation, but in the dark the complex is restored again, so that the complex could be defined as “photoreversible”. Furthermore, the PLLA-I₂ complex is thermoreversible as it dissociates when heated at +50 °C but the complex is restored in full when cooled down to +10 °C in the dark. With these quite unique photoreversible and thermoreversible properties the PLLA-I₂ complex behaves as a molecular switch i.e. a molecular system that can be reversibly interconverted between two states A and B by an external action or stimulus. Molecular switches are of key importance in nanotechnological applications.

PLLA与碘在三氯甲烷溶液中形成电荷转移（CT）络合物，Keq = 24.8±1.8 M ^-1，远高于模型化合物乳酸乙酯-碘在CHCl _3中测得的Keq = 0.75 M ^-1。PLLA-1 _2配合物的较高平衡常数表明特殊的聚合物-碘相互作用，这通过旋光分散（ORD）测量得到了证实，这是利用了PLLA是旋光聚合物的事实。实际上，ORD测量显示了在500 nm处产生的棉花效应，这进一步支持了溶液中PLLA链螺旋形线圈内部容纳的碘模型。PLLA-I ₂如果在黑暗和寒冷（+10°C）下保存，该复合物非常稳定。PLLA-I _2配合物在长时间保存后既显示电子光谱中CT带的增长，又显示ORD光谱中诱导的Cotton效应。但是，PLLA-1 ₂络合物对可见光敏感，并且在辐照下会解离，但是在黑暗中，该络合物又被还原，因此该络合物可以定义为“光可逆”。此外，PLLA-I _2配合物是热可逆的，因为在+50°C加热时会解离，但在黑暗中冷却至+10°C时会完全还原。凭借这些独特的光可逆和热可逆特性，PLLA-I ₂络合物的行为就像一个分子开关，即一个分子系统，可以通过外部作用或刺激在两个状态A和B之间可逆地相互转换。分子开关在纳米技术应用中至关重要。