用荧光方法研究端基为芘的聚苯乙烯在溶液中的聚集行为

Fluorescence Study on the Aggregation Behavior of Pyrene-end-capped Polystyrene in Solution

利用原子转移自由基聚合 (ATRP)方法合成了窄分布的端基含有芘或萘的聚苯乙烯 (Py PS和Na PS) .研究了Py PS在四氢呋喃 (THF)溶液中的荧光发射光谱随加水量的变化 .结果表明 ,加水初期随着加水量的增加 ,对应于芘的单体荧光发射峰强度 (IM)增加 ,当水加到一定量时 ,观察到由芘形成的激基缔合物 (excimer)的荧光光谱峰 ,其强度 (IE)随加水量的增加而进一步增强 ,而IM 下降 ,直至体系产生宏观的相分离 ,此时IM 和IE 均不变 .对这一结果从分子水平上进行了讨论 ,并通过IE/IM 与I1/I3 随加水量的变化得到了不同浓度下Py PS在THF中聚集的临界加水量 .另外 ,我们也用非辐射能量转移 (NRET)的方法研究了Py PS和Na PS混合溶液的聚集 .

Low polydispersive polystyrenes, tethered with pyrene (Py-PS) or naphthalene (Na-PS) at one end of the chain, were synthesized by atom transform radical polymerization (ATRP). The fluorescence emission spectra of Py-PS in THF were measured with different amount of water added. The results indicate that the 'monomer' fluorescence intensity (I M) of pyrene increased progressively with the increase of water content; and as the water content reached a certain amount, the emission of pyrene excimer was observed, whose intensity (I E) increased when water was further added, until a macroscopical phase separation appeared. The critical added water contents for Py-PS at three concentrations were obtained from the changes of I E/I M and I 1/I 3 with the addition of water. Nonradiative energy transfer (NRET) was also exploited for a mixture of Py-PS and Na-PS in THF. The results may help to understand the aggregation of PS, as well as copolymers containing polystyrene block in solution containing different amount of water.