含磷酰杂菲侧基聚苯乙烯的合成及其荧光性质

以2-(6-氧化-6-氢-二苯基(c,e)1,2氧杂磷酰基)-1,4-二羟基苯(ODOPB)结构单元为中心,在两侧通过酯化反应分别引入4-乙烯基苯甲酰基和4-戊氧基苯甲酰基,并作为苯乙烯衍生物单体(MED),在AIBN引发下,聚合得到了含9,10-二氢-9-氧杂-10-磷酰杂菲-10-氧化物(简称磷酰杂菲,DOPO)基团的聚苯乙烯衍生物(PED).因侧链之间具有较强的相互作用以及聚苯乙烯主链的刚性而易形成聚集形态,使分子量超出GPC的正常检测范围;同时表现出良好的热稳定性,MED和PED失重5%时的对应温度分别为339℃和345℃.也正是这两种作用同时存在,并相互制约,侧基之间产生了一定程度的规整排列,限制了磷酰杂菲基团的转动,降低了其非辐射能量转移,从而相对于MED,使PED在THF溶液中荧光强度得到了明显增强.由于PED在沉淀聚集过程中受到THF和沉淀剂(水或正己烷)的共同影响,在沉淀剂含量达到70%之前,侧基之间难以形成规整排列,其分子链内转动很大程度引起非辐射能量转移,所以随着沉淀剂含量的增加,荧光强度不断降低;然而当沉淀剂含量达到70%以上时,由于水分子能够与两个相互靠近的侧基共同形成基于氢键作用的复合超分子结构,这不仅抑制了磷酰杂菲基团的转动能力,增强了荧光强度,在一定程度上表现出AIEE特性,而且会在450nm处出现新的肩峰,以显示该结构有别于侧基自身的密聚集;但以正己烷为沉淀剂时,因不能形成氢键超分子结构,PED分子链只是无序密聚集,所以表现为只是随着正己烷加入荧光强度不断降低,没有出现荧光红移的现象。

SYNTHESIS AND FLUORESCENT PROPERTYIES OF PHOSPHAPHENANTHRENE-CONTAINING POLYSTYRENE

The introduction of phosphorus can effectively improve the flame retardancy,thermal stability,biocompatibility and other properties of polymers.The novel styrene derivant(MED) with phosphaphenanthrene side-group was first synthesized by means of two-step esterification of 2-(6-oxide-6Hdibenz < c,e > < 1,2 > oxaphos-phorin-6-yl)-1,4-dihydroxyphenylenes(ODOPB) as the center unit with 4pentyloxybenzoic acid and 4-ethenylbenzoic acid,respectively.The free-radical polymerization of MED initiated by AIBN was carried out for 12 h in THF solution.The yield of product(PED) is over 80%.Comparing with that of MED,the 1H-NMR spectrum of PED demonstrated that the polymerization of MED is realized successfully.Due to the strong π-π stacking and polar interaction between phosphaphenanthrene-containing pendent groups,as well as the rigid main-chain of polystyrene,PED can easily form aggregation state in polar solvents,such as DMF and THF,as a result the molecular weights of PED are beyond the detection range of GPC.At the same time,the TGA results reveal the excellent thermal stability of MED and PED because the temperatures are 339℃ for MED and 345℃ for PED at the 5% weight loss,respectively.For the induction of main-chain on the ordered arrangement and the strong interaction between the side-groups,the intramolecular rotation of phosphaphenanthrene groups in PED is more difficult than that in MED.So that,the non-radiative deactivation is decreased and the fluorescence intensity of PED in the pure THF solution is remarkably enhanced.With the addition of water or n-hexane,the fluorescence intensity of PED is induced to decrease because of the disordered aggregation between chains.When the water content was over 70%,the complexes based on the hydrogen bond bridge among a water molecule and two phosphaphenanthrene groups enhanced the intramolecular rotation restriction of some phosphaphenanthrene groups.Therefore,new shoulder peak at 450 nm is shown and the PL intensity increases.Clearly,the light emission of PED is induced by aggregating formation;in other word,PED is aggregation-induced emission(AIE)-active.When n-hexane as precipitant instead of water,the above-mentioned phenomenon is not shown in the absence of the formation of hydrogenbonded complex structure.The fluorescence intensity continuously reduced with increasing of the content of nhexane in the THF /n-hexane mixtures.The results allow us to design new materials with higher performance for chemo-and bio-detection applications.