ROMP polymerized systems

The use of porphyrinic ligands in polymeric systems allows their unique physio-chemical features to be integrated into two (2D)- or three-dimensional (3D) structures. As such, porphyrin or pc macrocycles have been extensively used to prepare polymers, usually via a radical polymerization reaction (85,86) and more recently via iterative Diels-Alder reactions (87-89). The resulting polymers have interesting materials and biological applications. For example, certain pc-based polymers have higher intrinsic conductivities and better catalytic activity than their parent monomers (90-92). The first example of a /jz-based polymer was reported in 1999 by Montalban et al. (36). These polymers were prepared by a ROMP of a norbor-nadiene substituted pz (Scheme 7, 34). This pz was the first example of polymerization of a porphyrinic macrocycle by a ROMP reaction, and it represents a new general route for the synthesis of polymeric porphyrinic-type macrocycles. 

The choice of a suitable initiator represents an important step in creating a well-defined polymerization system in terms of initiation efficiency and confrol over propagation. The entire system can only be designed on a stoichiometric base when a quantitative and fast initiation occurs. This is of enormous importance, because the composition of the entire polymerization mixture needs to be varied within small increments in order to control the microstructure. The catalyst needs to be carefully selected from both chemical and practical points of view. Schrock [5,10,12,109,110] and Grubbs systems [6], both highly active in the ROMP of strained functionalized olefins, can offen be used. Since fhe preparafion and in particu-... 

Floreancig [42] has described a new solid-phase linker system cleaved by oxidative electron transfer. The cleavage process is based on the oxidative fragmentation of homobenzylic ethers. Acetal 230, immobilized on a soluble oligonorbornene scaffold prepared by ROMP polymerization, was efficiently... 

ROMP techniques have certainly found their place in materials science. This has been made possible by adding well-defined and tolerant initiators to the armor of existing polymerization systems. With these initiators, in particular, ROMP and 1-alkyne polymerization have had an enormous impact on the development of both surface-modified and polymeric materials. Applications in catalysis and separation science have been added to the more traditional ones in optics and electronics. The ongoing developments in organometallic chemistry, in polymer chemistry, and, in particular, in metathesis polymerization will certainly result in the permanent improvement of existing systems and techniques as well as in new applications in many areas of chemistry and materials... 

The capability of ROMP of polymerizing even more complex functional monomers was demonstrated by the fact that the cationic NHC precursor l,3-di(l-mesityl)-4- [(bicydo[2.2.1 ]hept-5-en-2-ylcarbonyl)oxy]methyl -4,5-dihydro-lH-imidazol-3-ium tetrafluoroborate can be polymerized with the Schrock initiator Mo(N-2,6-f-Pr2-C6H3) (CHCMe2Ph)(OCMe(CF3)2)2 at ambient temperature in CH2CI2. The observed theoretical DP of 7 was in excellent accordance with a DP of 7 1 found via end-group analysis using H-NMR. The polymerization system fulfilled at least the requirements of a class-V living polymerization system. 

Despite the high mechanical and thermal stability of these stmctures, which are by far sufSdent for short- and medium-term analytical applications as wdl as applications in heterogeneous catalysis, " tert-allylic carbons located at the surface of a monolithic stmcture tend to be oxidized, resulting in a slow change of surface polarity of such monolithic columns. Consequently, the typical long-term stability of NBE-based, ROMP-derived columns is limited to less than 1000 injections. To solve this problem, a novel monomer/ cross-linker system had to be introduced. For these purposes, Buchmeiser et al. devdoped a polymerization system based on... 

Due to the aforementioned commercial successes of polymeric materials based on ROMP chemistry, olefin metathesis deservedly holds a place among the short list of successful polymerization processes. In addition, a number of ROMP polymer systems have been developed that possess useful properties, but a combination of feedstock pricing, process challenges, and lack of market pull have limited their use. However, because the markets for raw materials are dynamic and new applications for... 

Ring-Opening Metathesis Polymerization. Several new titanacyclobutanes have been shown to initiate living ring-opening metathesis polymerization (ROMP) systems. These have been used to make diblock and triblock copolymers of norbomene [498-66-8] (N) and its derivatives (eg, dicyclopentadiene [77-73-6] (D)) (Fig. 2) (41). 

Acyclic diene metathesis (ADMET) is a step-growth polycondensation reaction for the polymerization of o -dienes 729 The process is catalyzed by the same metal alkylidene initiators used for ROMP, and is driven by the removal of ethylene from the system (Scheme 13). Both molybdenum and ruthenium-based initiators have been used to prepare a variety of materials including functionalized polyethy-... 

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