Elsevier

Thin Solid Films

Volume 363, Issues 1–2, 1 March 2000, Pages 122-125
Thin Solid Films

Design, synthesis and photophysical properties of a hyperbranched conjugated polymer

https://doi.org/10.1016/S0040-6090(99)01013-5Get rights and content

Abstract

The conjugated dendrimer, poly(3,5-bisvinylic)benzene (HS1), was synthesized by two routes. Elementary analysis, FTIR, NMR and GPC spectra were used to characterize the dendrimer. HS1 has good solubility in common organic solvents although it does not contain long alkyl side chain. The photophysical properties in solution and net solid film are inspected. Absorption maxima were determined at 290 and 310 nm with a molar absorption coefficient in the order of 104, and the emission maxima were at 359 and 369 nm. The excitation spectrum is similar to that of the absorption. A mirror image relationship existed between the absorption and emission spectra characteristic of the rigid structure of the polymer. The Stokes shift (70 nm) is large, which means the large difference in the energy level between the ground and singlet excited state. The fluorescence quantum yield is about 36%. The net film of HS1 has a broad emission at 446 nm. The marked difference between the solution and net solid film in photophysical properties suggested the large change in intermolecular interaction from solution to the solid film state. Molecular mechanical calculations are used to aid the design and simulation of the structure of HS1. In generation 1–2, the optimized geometry shows a relatively good planarity. While the torsion appeared at the interference of the branches in generation 3 and the optimized geometry feels a zeolite structure. The calculation result is used to explain the experimental observation. The good photophysical properties and processing ability could make HS1 an ideal candidate in electroluminecence device as a blue emitter.

Introduction

Conjugated polymers [1] have emerged as viable electronic materials for numerous applications [2]. In particular, the current activities in the development of light-emitting diode (LED)-based conjugated polymers [3], [4], [5] have attracted much attention. Various new conjugated polymers have been designed and synthesized, for efficient light emission or charge transfer [6], [7], [8], [9], [10].

So far, the majority of work on polymers LEDs has been focused on linear one-dimensional polymer. Although a few of two-dimensional conjugated polymer, such as hyperbranched conjugated polymer have been reported to exhibit comparable charge transferring and processing properties to their linear counterparts, [11], [12], [13] two-dimensional conjugated polymeric light materials have been less discussed in the literature [14].

Dendrimers, including hyperbranched polymers, differ from conventional linear polymers in two critical ways. First, they are constructed from ABn required for hyperbranched structure the monomers rather than the standard AB monomers which produce linear polymers. Secondly, they are often synthesized in an interative fashion. The combination of these two features leads to a non-linear, stepwise synthetic growth wherein the number of monomer units incorporated in each of the successive interation roughly doubles (AB2) or triples (AB3) the existing branches. The novel structure of dendrimers is expected to produce unique properties [15], [16], [17].

Accordingly, conjugated dendrimers may be certain superior color tunabilty, charge transferring efficiency and processing properties than conventional linear emitting polymers. Therefore, we designed and synthesized various hyperbranched-conjugated polymers for potential materials applications.

In this report, we report on the synthesis and photophysical properties of a model compound, poly(3,5-bisvinylicbenzene) (HS1).

Section snippets

Experimental

The methods for preparing of the HS1 are outlined in Fig. 1. In route 1, tribromidemethylbenzene was condensated under the organic strong base. Route 2 is a Wittig reaction. Both are characterized by a low yield and a lower molecular weight. Especially for the route 2, the molecular weight is so small that oligomers were produced. So we only give results from route 1. The polymer structure shown is consistent with the element analysis and the spectroscopic date including 1H-NMR, 13C-NMR and

Results and discussion

It is very interesting to find that the polymer has a good solubility in chloroform, dichloromethane, THF, ethyl acetate etc, although the polymer contains no long alkyl chain. Good solubility has also been found for other hyperbranched conjugated polymers [17]. This unique properties may be attributed to their weak intermolecular interaction and low solvation energy.

The optical properties of this novel polymer are of primary interest to us. The photophysical data were listed in Table 1 and the

Acknowledgements

This project is supported by National Science Foundation of China (Nos 29992530 and 29873060) and A Key program of CAS (KJ97T-05-02).

References (19)

  • M. Halim et al.

    Synth. Met.

    (1997)
  • G. Grem et al.

    Synth. Met.

    (1992)
  • N. Tanigaki et al.

    Polymer

    (1997)
  • M. Meier et al.

    Synth Met.

    (1996)
  • M. Zheng et al.

    Photochem. Photobiol.

    (1998)
  • W.R. Salaneck et al.

    Conjugated Polymers and Related Materials: The Interconnection of Chemical and Electronic Structure

    (1993)
  • W.R. Salaneck et al.

    Science and application of conduction polymers

    (1991)
  • J.H. Burroughes et al.

    Nature

    (1990)
  • G. Gustafsson et al.

    Nature

    (1992)
There are more references available in the full text version of this article.

Cited by (45)

  • Amphiphilic hyperbranched polymers

    2019, Advanced Functional Polymers for Biomedical Applications
  • Hyperbranched aromatic polyesters: From synthesis to applications

    2010, Progress in Organic Coatings
    Citation Excerpt :

    Polycondensation of A2 + B3 system is a common technique that dates back at least to Berzelius as mentioned previously in the history of hyperbranched polymers. Thus, hyperbranched polyimides [32], polyesteramides [33], borate [34], poly-Schiff-base [35], triazine based polyamines [36], polyphenylenevinylene [37], polyarylamine-phenylene [38], and other structures like polyphenyloxindazole [39] have been reported now. Yan and Gao [40–42] developed a method known as couple monomer methodology (CMM) by modifying the A* + CB2 approach developed by DSM for Hybrane® [43] to the A2 + BB2′, A2 + CB2, AB + CDn, A* + Bn, and AA* + B2 approaches.

  • Chapter 4 Chain Structure Characterization

    2008, Comprehensive Analytical Chemistry
    Citation Excerpt :

    The molecular architecture of HBPs has lead to numerous potential applications of these materials like special classes of optical [139], magnetic [140], and conductive [141] materials. HBPs have also found applications in nano-composite films [142], as biomaterials [143] and molecular encapsulates [144]. One of the main reasons for the unique properties of HBPs is the molecular geometry of these disordered structures, in addition to their degree of branching, molecular weight, and polydispersity.

View all citing articles on Scopus
View full text