Copolymers of norbornene

Synthesis of block copolymers of norbornene derivatives, with different side groups, has been reported via ROMP [101]. Initially, exo-N-bulyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide was polymerized in acetone at room temperature with a ruthenium initiator (Scheme 40). The conversion of the reaction was quantitative. Subsequent addition of norbornene derivative carrying a ruthenium complex led to the formation of block copolymers in 85% yield. Due to the presence of ruthenium SEC experiments could not be performed. Therefore, it was not possible to determine the molecular weight... 

The living character of the ROMP promoted by the initiator Ru(CHPh)(Cl)2 (PCy3)2 (Cy = cyclohexane) was tested with the synthesis of diblock, triblock, and tetrablock copolymers of norbornene derivatives carrying acetyl-protected glucose, [2,3,4,6-tetra-O-acetyl-glucos-l-O-yl 5-norbornene-2-carboxylate], A or maltose groups, [2,3,6,2/,3/,4/,6/-hepta-0-acetyl-maltos-1-O-yl 5-norbornene-2-carboxylate], B, shown in Scheme 41 [102]. The AB, ABA, and ABAB structures were prepared by sequential addition of monomers with narrow molecular weight distributions to quantitative conversions. 

The first documented example of the living ROMP of a cycloolefin was the polymerization of norbornene using titanacyclobutane complexes such as (207) 510-512 Subsequent studies described the synthesis of di- and tri-block copolymers of norbornenes and dicyclopentadiene.513 However, functionalized monomers are generally incompatible with the highly electrophilic d° metal center. 

As a consequence of the living nature of the copolymerization wifh fhis catalyst, palladium-capped block copolymers of norbornene and ethene as well as of norbornene, ethene, and styrene were synthesized [61]. Higher activities (up to ten times higher) were observed for a series of oxazohne-phosphine complexes (e.g., 31). Several complexes, modified with bisphosphine monooxide and monosulfide ligands (Scheme 8.8, 32 and 33), were also used as catalysts precursors. The best reported turnover frequency is 0.6x10 mol (molh) at 80°C [62, 63]. A slightly lower activity was observed for fhe ketophosphine containing catalyst precursor 34 [64]. The activity of catalyst precursors 35, 36, and 37 is even lower [65]. 

Random copolymers of norbornene methyl-cyclopentyl ester and norbornene hexafluoro-isopropanol... 

FIGURE 16.10 Basic concept of Promerus product lines based on copolymers of norbornene derivatives. Different substituents are used to tailor specific polymer properties (R i = alkyl group, oxygen-containing group R2 = trialkylsiloxy group R3 = photosensitive ester group). 

The mechanical properties of these branched polymers are assumed to differ from those of metallocene/MAO-based COCs. " Other amorphous copolymers of norbornene and ethylene are also available using less active vanadium catalysts. ... 

Scheme XVII. Copolymer of norbornene and polyacelylene firom a metathesis-based precursor route.

Preparation 5-1 First, 5 units of norbornene, 25 units of maleic anhydride and 0.5 unit of 2,2 -azobisisobutyronitrile are placed in a reaction flask. Then, 200 ml of benzene as solvent is added. The mixture is agitated for 10 min, followed by a slow heating. Then, at 80°C, the mixture is allowed to react for 2 h. After filtration, a white solid compound can be obtained. This product is a copolymer of norbornene and maleic anhydride, with an average molecular weight of 4500 Dalton. 

Copolymers of norbornene with ethylene and/or lower linear olefins having repeat units (25) ... 

One or both monomers can be functionalized. Copolymers of norbornene with hexachlorocyclopen-tadiene 70 [Eq. (27)] will change the product properties considerably compared to the corresponding copolymer produced from norbornene and unsubstituted cyclopentadiene [49]. 

Similarly, copolymers of norbornene, with norbornene 0X0 derivatives such as those represented by (71) and (72), obtained in the catalytic presence of WClg/ Me4Sn, display properties totally different from those of the homopolymers [50] ... 

Other polymers with properties similar to those of picarin include a copolymer of norbornene and ethylene (NEC), which has a transmission of about 90% (for a 2 mm-thick sample) in the frequency range between 0.2 and 1.2THz [111], and poly(4-methyl pentene-1) (TPX Mitsui Chemicals). The latter is transparent at UV, visible and far-IR frequencies [112]. The chemical structures of the base units of these polymers are provided in Chart 2.13. 

Random copolymers of norbornene melhylcyclo-penlyl ester and norbornene hexafluoroisopropa-nol... 

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