Side-chain functionalization polymers

Carlise JR, Week M. Side-chain functionalized polymers containing bipyridine coordination sites polymerization and metal-coordination studies. J Pol3mi Sci Part A Polym Chem 2004 42 2973-2984. 

Pollino JM, Week M. Supramolecular side-chain functionalized polymers synthesis and self-assembly behavior of polynorbornenes bearing Pd SCS pincer complexes. Synthesis 2002 9 1277-1285. 

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). 

An interesting dimension of metal-coordinated self-assembly that is often ignored, or at least not exploited to its fullest extent, occurs when the resulting coordination complex is a charged species and, as such, in need of a counterion. This counterion itself presents yet another subtle instance of ionic self-assembly, which often is overshadowed by its partner, the coordination complex. The second multi-functional side-chain supramolecular polymer system is based on this simple but important concept [14, 106-111]. In 2003, Ikkala and coworkers reported a study in which they exploited (1) a side-chain functionalized polymer, poly(vinyl-pyridine), (2) metal-coordination self-assembly via a tridentate Zn2+ complex and (3) ionic self-assembly through functionalized counterions, i.e. dodecylbenzene-sulfonate ions, to form multiple self-assembled complexes which adopted a cylindrical morphology (Fig. 7.23) [112]. 

Due to the rather easy accessibility of novel functional polymer materials by click reactions, their potential scope of applications has significantly broadened in the last years. Through the preparation of functional thin polymer films, biohybrids, or self-assembly structures from end group or side chain functionalized polymers and functional block copolymers, applications, for example, as adhesives or additives, but especially also in optoelectronics, biomedicine, drug delivery, biochips, and micro- and nanoelectronics become accessible. 

As an alternative, side-chain functionalized polymer chains can associate by (c) low molecular weight crosslinkers or (d) mutual heterocomplementary polymer-polymer binding... 

Figure 24 Schematic representation of the noncovalent assembly of dendronized side-chain functional polymers. Reproduced from ten Cate, A. T. Kooijman, H. Spek, A. L. etal. J. Am. Chem. Soc. 2004, 126,3801-3808. ...

The preparation of side-chain functional polymers bearing important supramoiecuiar motifs has proven to be of great importance as these materials act as effective platforms for the development of a wide variety of functional, supramoiecuiar systems. 

Zimmerman and coworkers made use of complementary quadruple hydrogen-bonding complexes to form networks and blend two different side-chain functionalized polymers, poly(butyl methacrylate) (PBMA, marked in light blue) and PS (marked in red. Figure 5). The polymer blends were characterized by differential scanning calorimetry (DSC),... 

The copper-catalyzed azide/alkyne click reaction has found the broadest application in the modification of ROMP polymers, with the first reported example in 2004 by Binder and Kluger [13]. Since then, the copper-catalyzed click reaction has been used for the preparation of block copolymers [24, 29, 37], stars [18, 26], cycles [23], networks [25], and graft copolymers [27, 28, 38, 56, 57], as well as for end- [16] and side-chain-functionalized polymers [13, 17, 19-22, 48]. The most often used catalysts and bases for the azide/alkyne click reaction include copper(l) iodide, copper(l) bromide, trisftriphenylphosphine) copper(l) bromide, or copperfll) sulfate/sodium ascorbate as catalyst and diisopropylethylamine (DIPEA), pentamethyldiethylenetriamine (PMDETA), or 2,2 -bipyridine (bPy) as base. 

A recent example from Haddleton and coworkers combined sugar and non-sugar ligands to use secondary binding effects to enhance not only the overall affinity, but also the specificity of the glycopolymer. In the process, they developed a new 3-step tandem post-polymerization protocol based on an epory side-chain functionalized polymer, as shown in Figure 2.21. 

Fig ure 2.20 Synthesis of heteromultivalent glycopolymer via a coclicking approach on an alkyne side chain functional polymer. ... 

Bunl994a Bunin, B.A. and Ellman, J.A., Increasing the Diversity of a 1,4-Benzodiazepine Library Through Side-Chain Functionalization, Polymer Preprints, 35 (1994) 983-984. 

Cationic polymerisation has also been utilized to produce side-chain functional polymers. HOS and MOS can by cationically copolymerised either in a random or block fashion under /CH3CN,CH2Cl2/BF30Et2, water/0°C/// conditions (2.6 < Mn/(kg/mol) < 6.5 1.28 < Mw/Mn < 1.48). The hydroxy group does not have to be protected for polymerisation under these conditions [84]. 

In addition to the alkene-functionalized polymer approach of making side-chain functionalized polymer, other approaches have also been reported. For example, based on the protection-deprotection chemistry of ortho-nitrobenzyl moiety, Barner-Kowollik and coworkers investigated light-triggered release of thiols at ambient temperature and developed a novel method to modify functionalization... 

---