Polymerization substituted norbornenes

Multi-component catalyst systems based on palladium compounds and phosphorus compounds show a particularly high activity (35). The high catalytic activity is not deteriorated in the course of polymerization. Substituted norbornene derivates can be used that are otherwise difficult to polymerize. 

Fig. 14. A,B. A living polymerization of mannose-substituted norbornene derivatives can be used to produce materials of defined lengths for biological testing. B The relationship between polymer length and biological activity was explored...

As had been observed in the synthesis of carbohydrate-substituted polymers of different lengths, the reactivity of the monomers was an important parameter in generating the triblock polymers. If the mannose-substituted 7-oxanor-bornene derivative was first polymerized, followed by the galactose-derivatized norbornene and the mannose-substituted norbornene monomers, two distinct sets of products were observed. These were identified by modification of the resulting polymers by acetylation, and analysis of the products by GPC. With this protocol, it was found that the product was composed of short polymers (DP=... 

As shown by H NMR, the activated catalyst mixture reacts with norbornene (or a series of methyl-substituted norbornenes) to be partially converted to a new carbene species [53]. From the ratio of product carbene and residual initiator carbene concentrations, it was estimated that the rate constant for propagation is at least 3 times that for initiation. The three species present in the equilibrium situation of Eq. (39) may all possess their own intrinsic activities, resulting in a more complex polymerization behavior. In addition, a substantial amount of secondary metathesis occurs, as shown by changes in both the cis content of the polymer and head/tail ratio of the substituted carbenes when the catalyst was left in solution (120 min at 20 °C) after consumption of the monomer. 

Synthetic methods targeting amino acid incorporation into functional materials vary widely. Free-radical polymerization of various amino acid substituted acrylates has produced many hydrocarbon-amino acid materials [161, 162]. In separate efforts, MorceUet and Endo have synthesized and meticulously characterized a library of polymers using this chain addition chemistry [163- 166]. Grubbs has shown ROMP to be successful in this motif, polymerizing amino add substituted norbornenes [167-168]. To remain within the scope of this review, the next section wiU focus only on ADMET polymerization as a method of amino add and peptide incorporation into polyethylene-based polymers. 

Aqueous insertion-type polymerization of norbornene and substituted derivatives [Eq. (7)] has also been investigated. The tolerance of norbornene polymerization using [Pd(NCCH3)4](BF4)2 as an initiator towards added amounts of water was noted by Risse and Mehler in 1992 [91]. 

These complexes also functioned well in benzene, although small amounts of ethanol were necessary to initiate polymerization. The order of activity for these catalysts was Ir(III) > Os(III) > Ru(III), and they were found to polymerize monomers with exo substituents more readily than endo isomers. Rinehart and Smith later demonstrated that these complexes initiated the aqueous polymerization of a substituted norbornene derivative in the presence of anionic emulsifiers and suitable reducing agents [24]. This reaction gave particularly low yields of polymer (typically less than 9%), but the overall tolerance of these complexes to polar and protic functionalities made them ideal candidates for further study. 

Fig. 94 Polymerization of norbornene derivatives geminally substituted with CF3 and C02tBu...

One of the first examples of Lewis-acid-free initiators based on tungsten I), W(0-2,6-i-Pr2-C6H3)2Cl2-(CH-t-Bu)(OR)2, (R = Et, i-Pr), which allowed the polymerization of substituted norbornenes, was reported by J. M. Basset and co-workers. Additionally, Lewis-acid-free W(=C(CH2)4)(OCH2-f-Bu)2Cl2 was reported to effectively polymerize substituted nor-bomenes such as exo-norbom-5-ene-2,3-dicarboxylic anhydride. Finally, the synthesis of the aryloxy— alkyloxy tungsten alkylidene complex reported by Basset et al. needs to be mentioned (Scheme 2). The... 

When conducting the ROMP of norbornene or cyclooctadiene in miniemulsions [82], two approaches were followed (i) addition of a catalyst solution to a miniemulsion of the monomer and (ii) addition of the monomer to a miniemulsion of Grubbs catalyst in water. With the first approach it was possible to synthesize stable latexes with a high conversion, whereas for the second approach particles of >400 nm were created, without coagulum, but with 100% conversion. Subsequently, a water-soluble ruthenium carbene complex [poly(ethylene oxide)-based catalyst] was prepared and used in the direct miniemulsion ROMP of norbornene [83], whereby particles of 200-250 nm were produced. The catalytic polymerization of norbornene in direct miniemulsion was also carried out in the presence of an oil-soluble catalyst generated in situ, or with a water-soluble catalyst [84] the reaction was faster when using the oil-soluble catalyst. Helical-substituted polyacetylene could be efficiently polymerized in direct miniemulsion to yield a latex with particles that ranged between 60 and 400 nm in size, and which displayed an intense circular dichroism [85] that increased as the particle size decreased. The films were prepared from dried miniemulsion latexes that had been mixed with poly(vinyl alcohol) (PVA) in order to conserve the optical activity. 

COMA polymers (Fig. 17), synthesized by conventional radical polymerization, have a 1 1 alternating structure, a consequence of the preference for each radical to react exclusively with the other monomer. As a rnle, the products are high Tg materials for example poly(norbornene-co-maleic anhydride) has a Tg > 300°C. The polymerization allows the incorporation of small amoimts of other vinyl monomers (e.g. acrylic acid) without disruption of the alternating structure (117). Substituted norbornenes can be included in the pol5mierization mixture to incorporate acid-labile functionality, to modify polymer polarity, and to improve film adhesion (118). Cholate dissolution inhibitors can be added in the formulated resist to further modify functional properties (119). 

Halogen-substituted Norbornenes. Fluorinated norbornenes have been polymerized with classical systems, e.g., WCl6/SnMe4 or MoCl5/SnMe4 [456] but also with alkylidene compounds, e.g., Schrock catalysts [457,458], Fluorinated norbornadienes show the same behaviour [458],... 

The present paper reports the ring-opening polymerization of norbornene derivatives substituted by nitrile, amide, imide, ester, pyridyl and acid anhydride groups by the above-mentioned catalysts. The polymerization behavior of these monomers and the physical properties of the polymers of norbornenenitriles will be described. 

Similar micro structures are obtained when norbornene is replaced by norbomadiene. 5-and 6-substituted norbornene derivatives when polymerized by ROMP give more complex micro structures (Figure 11). By ROMP it is possible, more easily than by Ziegler-Natta catalysts, to polymerize norbor-nenes with polar substituents such as carbomethoxy, carboethoxy, or trifluoromethyl groups. " ... 

Wolfe and Wagener have developed main-chain boronate polymers (59) (Fig. 38) by the acyclic diene metathesis (ADMET) polymerization of symmetrical ,oj-dienes, containing both methyl- and phenyl-substituted boronate functionalities using Mo and Ru catalysts.84 The ring-opening metathesis polymerization (ROMP) of several norbornene monomers containing methyl- and phenyl-substituted boronates into... 

The earliest reported ring-opening polymerizations of functionalized norbornenes were carried out in protic solvents (alcohol, water) using iridium, ruthenium, or osmium salts. Thus, norbornenes substituted with ester (93-95), hydroxy (95), chlorine (96), alkoxy (97), and imide (93) groups have been polymerized via metathesis using noble metal catalysts. 

The alkyl-substituted titanium carbene complex 18 reacts with norbornene 24 to form a new titanacycle 25, which can be employed for the ROMP of 24 (Scheme 14.13). The titanacycle generated by the reaction of the Tebbe reagent with 24 is also used as an initiator for the same polymerization [23]. These preformed titanacyclobutanes also initiate ROMP of various other strained olefin monomers [24],... 

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