Side-chain multifunctional polymer

An example of a side-chain multifunctional polymer is a photorefractive polymer shown in Figure 3. 

In 2004, Week and co-workers demonstrated that both mono- and multifunctional self-assembly could be employed simultaneously independently and reversibly on the same side-chain functionalized polymer [96]. A random terpolymer of poly(norbornene) was synthesized consisting of diaminopyridine (DAP) hydrogen-bonding receptors and a palladium-functionalized SCS-type pincer ligand for metal coordination-based self-assembly (Fig. 7.18). 

Figure 3. The structure of a multifunctional side chain photorefractive polymer.

Supramolecular polymers can be divided into two main categories, namely main-chain and side-chain supramolecular polymers. Additionally, networks can be obtained using multifunctional moieties [7]. A schematic overview is shown in Figure 4.1. 

The multifunctional initiators may be di- and tri-, azo- or peroxy-compounds of defined structure (c.g. 20256) or they may be polymeric azo- or peroxy-compounds where the radical generating functions may be present as side chains 57 or as part of the polymer backbone."58"261 Thus, amphiphilic block copolymers were synthesized using the polymeric initiator 21 formed from the reaction between an a,to-diol and AIBN (Scheme 7.22).26 Some further examples of multifunctional initiators were mentioned in Section 3.3.3.2. It is also possible to produce less well-defined multifunctional initiators containing peroxide functionality from a polymer substrate by autoxidalion or by ozonolysis.-0... 

The expected contribution of catalysis in this area will derive both from the availability, at low processing costs, of new monomers obtained from biomasses and from the development of an optimized combination of biotechnology processes with classical and new biocatalytic processes. Research priorities for catalysis in the area of polymers from renewable materials for packaging, furniture, domestic water purification and recycling include the need to develop novel catalysts, e.g., for functionalization of polymeric and dendrimeric materials, with side-chain photoactive molecular switches (to be used as smart materials), or the development of multifunctional materials, combining, for example, nanofiltration with catalytic reactivity. 

The self-assembly of the various polymer systems described in the above sections is only a brief summary of the attempts by chemists to create multifunctional materials based on noncovalent interactions. The unique regions present within a polymer including the (1) main-chain/backbone, (2) end groups, (3) side-chains and (4) dendritic periphery, along with the ability to functionalize any of these regions with recognition units, provide chemists with a wide array of self-assembly possibilities with which to build and create multifunctional materials. 

Side-chain liquid-crystalline polymers with controlled molecular weights have been obtained by the polymerization of FM-25 with 1-22 (X = Br)/CuBr/ L-3 in the bulk at 100 °C, to examine the thermotropic transition as a function of the MWD.324 Second-order nonlinear optical materials with branched structure were prepared by the copper-catalyzed radical polymerization of FM-26 and FM-27 using hyperbranched poly[4-(chloromethyl)styrene] as a multifunctional initiator.325... 

To improve the luminance efficiency of PLEDs, many research groups have attached electron and/or hole transport moieties on the side chain of the polymer backbone or on the main chain of the polymer. Therefore, we reported a new series of multifunctional high-brightness and luminance-efficient EL polymers, poly[2- 4-[5-(4-(3,7-dimethyloctyloxy)phenyl)-l,3,4-oxadiazole-2-yl]phenyloxy -l,4-phenylenevinylene] (Oxa-PPV), DMOP-PPV,... 

In a branched polymer, some monomers become part of side chains, branching off the main chain or off other branches. Monomers with a functionality of three or greater may form branched polymers, since three parts of the polymer molecule can extend from a single monomer wherever a trifunctional monomer is located. The degree of branching of the polymer will depend on the number of multifunctional monomers present during the reaction. 

Here, we have designed and synthesized multifunctional poly(bithienylene-phenylene)s with either racemic (Poly-9) (M — 14,000) or chiral moieties ((/ )-/ (S)-Poly-lO (Mn = 10,000, 8,000, respectively), which exhibit fluorescence, liquid crystallinity, and photoresponsive properties (Fig. 11.20). The polymers are composed of a 7t-conjugated main chain, poly(bithienylene-phenylene), which acts as a fluorescence moiety and mesogen core, and photochromic DE moieties [71, 72] are linked with racemic or chiral alkyl groups in the side chains. The DE photoresponsive moiety isomerizes between its closed and open forms upon irradiation of UV and visible light, respectively. 

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