【作者】 张孝阿；

【导师】 孙景志； 唐本忠； 秦安军；

【作者基本信息】 浙江大学 ， 高分子材料， 2012， 博士

【摘要】 功能化聚炔的设计合成一直是聚炔领域的研究热点之一。作为最简单的聚炔,聚乙炔便以其掺杂导电性闻名于世。聚炔侧基含有功能性基团时,聚合物整体可以表现出相应的功能,如液晶性、发光性、光学非线性、光学活性、溶致变色性、亲水性、生物活性等。通过控制侧基上功能基团与主链的连接方式(直接相连、刚性链相连、柔性链相连),可调节二者之间的相互作用(如电子效应、空间效应、电荷或能量转移等),使聚炔的功能化更加复杂多样。然而,将功能基团接到聚炔侧基的指定位置,得到结构和分子量及其分布可控的功能化聚炔,并非易事。原因有二：(1)炔烃聚合本身的不可控性,即单体结构、催化剂和溶剂的种类会对聚合结果产生无法预知的影响；(2)催化剂对功能基团的耐受性很差,尤其是双取代炔烃聚合必须使用的易位催化剂,遇到含活泼氢的极性基团会中毒失效。为了系统研究功能化聚炔结构-性能关系,在开发新型催化剂、完善直接聚合法的同时,也有必要探索制备功能化聚炔的类似于模版法的新方法。本论文首先以有机铑络合物[Rh(diene)Cl]2为催化剂合成了带四种侧基含偶氮苯液晶基元的聚苯乙炔衍生物P1(6)、P2(6)、P1(12)和P2(12),其化学结构与预期一致,分子量及其分布适当。研究了四种聚炔的光致异构化行为、热稳定性和液晶性,讨论了刚性主链、偶氮苯结构和柔性烷基间隔链三者对聚合物性质的影响。结果表明：刚性主链和偶氮苯基元之间的柔性烷基链对聚合物光致异构化的速率和液晶相的形成有很大影响。烷基链由C6变为C12时,不但异构化速率加快,而且能够形成各向异性的POM图像。此外,偶氮苯基元上的三氟甲基对形成典型的SmA液晶相有较大贡献。据XRD数据和理论计算结果推断聚炔主链与侧链呈“鱼骨”状,偶氮苯基元连在侧链末端,且相邻基元之间以“插指”模式平行排列。这些结论在一定程度上揭示了聚合物主链、柔性间隔基和偶氮苯功能团之间的相互作用,有助于进一步构筑新型的功能化共轭聚合物。本论文进一步探索了反应性侧基在合成单取代功能化聚炔中的作用,拓展了聚炔侧基后功能化的范围。选择有机铑络合物为催化剂,设计合成了三种侧基含五氟苯酯结构的聚苯乙炔衍生物P1、P2和P3,而后利用五氟苯酯与有机胺的亲核取代反应,将亲水性PEG链、疏水性烷基链、手性碳等功能性结构引入聚合物侧基上,得到十八种单取代功能化聚炔。红外和核磁结果与预期一致,并且证明了活性酯的取代具有便捷、定量转化、无副反应等特性。GPC结果表明,所得功能化聚炔的分子量及其分布与相应的母体聚合物高度一致。我们进一步实施了两种功能性胺(如亲水性的氨基PEG和疏水性的烷基胺)与活性酯聚炔反应,得到了双重功能化的聚炔,1H NMR结果表明聚合物侧基中两种功能基团的比例与两种胺的投料比是一致的。因此,我们可以通过控制两种后功能化试剂的比例，定量地调节聚炔侧基双重功能化的程度,得到类似于两种炔单体无规共聚的产物。研究发现,侧基上的手性碳能够诱导聚炔主链呈螺旋构象,并且诱导螺旋的能力与手性碳构型、手性侧基比例和手性碳与主链的连接方式有关：第一,构型相反的手性碳诱导主链呈方向相反的螺旋构象；第二,手性侧基的比例越低,聚炔溶液测得的圆二色(CD)信号强度越小,但是手性侧基间的协同性(cooperativity)较弱,因而没有明显的手性放大效应；第三,当聚苯乙炔主链与手性碳之间有C5和C10烷基间隔链时,聚炔溶液检测不到CD信号,这说明手性碳与聚苯乙炔主链直接相连是手性诱导的充分条件。研究还发现,侧基含PEG链的聚炔具有两亲性和温敏性。一方面,PEG功能化聚炔能够溶于水形成表观澄清的溶液,但是核磁结果表明只有PEG链溶解,而疏水部分被包裹在内。PEG链的引入也使得聚炔薄膜的接触角大幅度下降,出现疏水性到亲水性的转变,而PEG链和烷基间隔链的长度分别对亲水性起积极和消极作用,并且亲水性侧基的含量也对聚炔的亲水性有很大影响。另一方面,PEG赋予聚炔LCST行为,PEG链越长浊点越高,烷基间隔链越长浊点越低。在此基础上,本论文将活性酯策略运用到双取代聚炔的侧基功能化改性中。首先选用W催化剂合成了侧基含五氟苯酯的聚二苯乙炔衍生物(P4),之后与多种手性胺反应得到侧基含羟基、酯基、羧基等高极性基团的功能化聚二苯乙炔(P5-P10),而由于催化剂中毒问题,含高极性基团的双取代炔单体无法直接聚合得到聚合产物。同样用红外和核磁表征了单体和聚合物的结构，结果与预期一致,确定无疑地证实了活性酯侧基后功能改性可用于双取代聚炔领域。研究发现,不同结构的手性碳具有不同的诱导主链螺旋的能力,同时由于侧基结构不同,导致主链共轭长度改变,所以不同功能化聚炔的荧光发射性质有所不同。水分的不断加入使得聚炔分子发生聚集,而不同侧基基团对分子聚集的影响不同,具体可归结为短程相互作用的增强和苯基发色团内旋转受阻两个方面,最终导致聚炔溶液的荧光强度发生先增大后减小的变化。利用活性酯法将芘结构引入聚合物侧基上,得到两种单取代聚炔(P12和P13)和两种双取代聚炔(P14和P15)。由于侧基含芘,四种聚炔的紫外吸收都表现出聚炔主链与芘叠加的性质,然而它们表现出不同的荧光发射性质。单取代聚炔P12和P13的聚合物主链不发光,所以荧光光谱中只出现侧基芘的“单体”和“激基缔合物”在400和480nm附近的发光。对于双取代聚炔P14和P15,343nm激发时,由于存在芘“单体”“激基缔合物”和主链三个潜在发光物种,并且发生了从侧基芘到主链的荧光共振能量转移,所以芘“激基缔合物”的发光消失,芘“单体”的发光明显减弱,而主链的发光比380nm激发时增强了2-3倍。另外,除了主链结构外,芘发色团与主链的连接方式对聚炔的荧光发射性质也有影响。当芘直接连于单取代聚炔主链时,聚合物(P12)更多地表现为“激基缔合物”的发光,而含C10烷基间隔链的聚炔(P13),芘“单体”的发光明显增强。双取代聚炔中,C5烷基间隔链也有助于芘“单体”发光的增强。更多还原

【Abstract】 The design and synthesis of functional polyacetylenes has been a hot topic in the field of polyacetylenes. Polyacetylene, with the simplest structure, is famous for its outstanding electrical conductivity. Generally, functional side groups can endow the whole polymer with corresponding functionality, such as liquid crystallinity. light emission, optical nonlinearity, optical activity, solvatochromism, hydrophilicity, and biological activity. Even versatile functionalities can be achieved by adjusting the interaction between polymer backbone and functional side groups, i. e. electronic interaction, steric effect, charge transfer, or energy transfer. However, functional groups are usually not easy to be attached to the desired position in the side chain. On one hand, the controlled polymerization of acetylenic monomers has not successfully been achieved with nomal catalysts; On the other hand, the polymerization catalysts, especially the metathesis catalysts, are intolerant of polar functional groups in the monomers. Therefore, it is necessary to develop new platform-like synthetic route toward various functional polyacetylenes, besides catalyst development and direct polymerization implementation, in order to systematically study the structure-property relationship.Four azobenzene-bearing polyphenylacetylenes, P1(6), P2(6), P1(12), and P2(12) were synthesized by using organorhodium complexes [Rh(diene)Cl]2as catalysts. Their photoinduced isomerization behavior, thermal stability, and liquid crystalline property were carefully studied. Results show that longer alky] spacer contributes to quicker isomerization rate and is essential to the formation of anisotropic liquid crystal phase. In addition. the mesophase was assigned to SmA phase when the azobenzene is attached with trifluoromethyl. Combind XRD results and theoretical calculation, we believe that a single polymer chain takes a fishbone configuration with a mesogen at the end of each side chain. The mesogens on the adjacent polymer side chains take an interdigital arrangement. In summary, this work demonstrated the interdependent properties between three key structural parameters of rigid polymer backbone, flexible alkyl spacer, and photoisomerization-capable mesogen. thus provides helpful information to the designation and preparation of conjugated polymers with desirable opto-electronic properties.We further explored the role of reactive pendants in the functionalization of monosubstituted polyacetylenes. Pentafluorophenyl (PFP) ester-functionalized poly(phenylacetylene)s (PPAs, P1, P2and P3) were designed and synthesized in desirable yields and molecular weight by using organorhodium complexes as catalysts. These PFP-containing PPAs were further used as precursors to prepare a series of18mono-and dual-functionalized PPAs by the substitution of the activated ester moieties with functional amines. The experimental details and the IR and NMR characterization data demonstrate that activated ester synthetic route to functional PPAs is facile (just stirring the precursor polymer with proper amine(s) at room temperature for hours), efficient (complete transition from ester to amide has been confirmed), and quantitative (the relative content of a specific functionality can be precisely preset by controlling the feed ratio of the functional amines). CD measurements indicated that the incorporation of chiral amine into polymer side chains induced helicity formation of P1backbone. P1-C*Ph(L) and P1-C*Ph(D) backbones adopt predominantly right-handed and left-handed helical conformation. respectively. While the flexible spacer between the chiral center and the rigid PPA backbone blocked the induction of main-chain helicity by chiral pendants, thus no CD signals were recorded for P2-C*Ph(L) and P3-C*Ph(L). Substitution of PFP ester with amine-functionalized PEGs transited the hydrophobic PPAs to hydrophilic. All of the PEG-contain ing PPAs can be dissolved in water and form clear solutions. Meanwhile, all of the aqueous solutions exhibit LCST behavior and the hydrophilic PEG chains and hydrophobic alkyl spacers have positive and negative impact on the cloud point, respectively. Contact angles measurements showed that the length and content of the PEG chains contribute greatly to the hydrophilic property, and the length of the alkyl spacers and the content of the alkyl amine component played a contrary role. By controlling the ratio of the PEGylated and alkyl amines, the amphiphilic property of the PPAs can be well tailored.Activated ester strategy was further utilized to synthesize functional disubstituted polyacetylenes. which contains highly polar groups on their side chain and can not be obtained through direct polymerization with metathesis catalysts. A pentafluorophenyl (PFP) ester-containing diphenylacetylene was designed and polymerized to obtain PFP activated ester-functionalized disubstituted polyacetylene (P4). P4was used as a parent polymer to further react separately with diverse amines, giving rise to a series of functional disubstituted polyacetylenes (P5-P10) with chiral moiety, and/or hydroxyl. carboxyl groups in high yields under mild condition. Spectral characterization data indicated that the polymers" structures were well consistent with the expected results. The helicity and emission property of polymers were also studied. Results show that different chiral structure has different ability to induce backbone helicity, and postfunctionalization cause different conjugation length and different emission property.Pyrene was incorporated into the side chain of four polyacetylenes through activated ester strategy, obtaing two monosubstituted (P12and P13) and two disubstituted (P14and P15) pyrene-containing polyacetylenes. Excited at343nm, P12and P13emit around400and480nm, which is ascribed to the pyrene "monomer" and "excimer" respectively. However, the emission property of P14and P15is rather complicated, because fluorescence resonance energy transfer (FRET) is occurred from pyrene to polymer backbone. When excited at380nm, only the polymer backbone emits around510nm. When excited at343nm, there are three kind of potential emissive species, i. e. pyrene "monomer", pyrene "excimer". and polymer backbone. However, the PL spectra only show two emission peaks around400and510nm which can be ascribed to pyrene "monomer" and polymer backbone respectively. The pyrene "excimer" emission is completely disappeared and the "monomer" emission is weaker, but the backbone emission intensity is2-3times stronger than excited at380nm.更多还原