Olefin monomers

As a general rule, olefin-MA copolymerizations, run in the presence of free-radical initiators, give only equimolar copolymers (see Chapter 10). However, conditions are known where random copolymers may be prepared that contain less than equimolar amounts of MA. For example, high-pressure, free-radical-initiated copolymerization of ethylene with 3% MA or 2-3% monomethyl maleate has been used to prepare ionomer-type materials. 

Esters of endomethylene tetrahydrophthalic anhydride and other derivatives of norbornene are known to form eutectic mixtures with Ma/ 2.73.340,341,374-379) SQij j.gtate copolymerizatiou of the eutectic mixture of monopropyl endomethylene tetrahydrophthalate and MA, using Co y-ray initiation, produces nonequimolar copolymer. Neither monomer homopolymerizes under the experimental conditions used. It is believed that copolymerization of the monomer mixture is made possible by the increased 

A Ziegler catalyst system composed of diethylaluminum chloride and titanium chloride in toluene at 0 C has also been claimed useful for preparing vinyl ether-MA copolymers. In typical experiments, the reactions were terminated after 3 h by adding methyl alcohol, and the product was purified by precipitation with excess alcohol. The yields vary with proportion of comonomers, 98% for a 7 1 mole fraction of isobutyl vinyl ether-MA, 92% for a 2-4 1 mole fraction, but only 44% for a 1 1.2 mole fraction. Similar 

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Hydrocarbon resin is a broad term that is usually used to describe a low molecular weight thermoplastic polymer synthesized via the thermal or catalytic polymerization of coal-tar fractions, cracked petroleum distillates, terpenes, or pure olefinic monomers. These resins are used extensively as modifiers in the hot melt and pressure sensitive adhesive industries. They are also used in numerous other appHcations such as sealants, printing inks, paints, plastics, road marking, carpet backing, flooring, and oil field appHcations. They are rarely used alone. 

With the improvement of refining and purification techniques, many pure olefinic monomers are available for polymerization. Under Lewis acid polymerization, such as with boron trifluoride, very light colored resins are routinely produced. These resins are based on monomers such as styrene, a-methylstryene, and vinyltoluene (mixed meta- and i ra-methylstyrene). More recently, purified i ra-methylstyrene has become commercially available and is used in resin synthesis. Low molecular weight thermoplastic resins produced from pure styrene have been available since the mid-1940s resins obtained from substituted styrenes are more recent. 

Ethylene has also been copolymerised with a number of non-olefinic monomers and of the copolymers produced those with vinyl acetate have so far proved the most significant commercially . The presence of vinyl acetate residues in the chain reduces the polymer regularity and hence by the vinyl acetate content the amount of crystallinity may be controlled. Copolymers based on 45% vinyl acetate are rubbery and may be vulcanised with peroxides. They are commercially available (Levapren). Copolymers with about 30% vinyl acetate residues (Elvax-Du Pont) are flexible resins soluble in toluene and benezene at room temperature and with a tensile strength of about lOOOlbf/in (6.9 MPa) and a density of about 0.95 g/cm. Their main uses are as wax additives and as adhesive ingredients. 

Despite the utmost importance of physical limitations such as solubility and mixing efficiency of the two phases, an apparent first-order reaction rate relative to the olefin monomer was determined experimentally. It has also been observed that an increase of the nickel concentration in the ionic phase results in an increase in the olefin conversion. 

In the homogeneous Dimersol process, the olefin conversion is highly dependent on the initial concentration of monomers in the feedstock, which limits the applicability of the process. The biphasic system is able to overcome this limitation and promotes the dimerization of feedstock poorly concentrated in olefinic monomer. 

ROMP is without doubt the most important incarnation of olefin metathesis in polymer chemistry [98]. Preconditions enabling this process involve a strained cyclic olefinic monomer and a suitable initiator. The driving force in ROMP is the release of ring strain, rendering the last step in the catalytic cycle irreversible (Scheme 3.6). The synthesis of well-defined polymers of complex architectures such as multi-functionaUsed block-copolymers is enabled by living polymerisation, one of the main benefits of ROMP [92, 98]. 

Coordination polymerization Can engineer polymers with specific tacticities based on the catalyst system Can limit branching reactions Polymerization can occur at low pressures and modest temperatures Otherwise non-polymerizable monomers (e.g., propylene) can be polymerized Mainly applicable to olefinic monomers... 

Other additives can promote chain reactions by acting as initiators of the chain. These compounds are materials that can be more readily dissociated than the primary reactants. For example, benzoyl peroxide has often been used to initiate the polymerization of olefinic monomers because of the ease with which it dissociates. 

With the exception of LDPE, polyolefins like other polyethylenes and polypropylene, which represent the largest amount of vinyl-type polymers produced in the world, are neither synthesized by radical nor by classical ionic polymerisation processes. Different types of polymerisation catalysts are in use for these purposes. The Cr-based Phillips catalyst, Ziegler-Natta type catalysts, metallocene or other more recently discovered catalysts, including late transition metal catalysts, are all characterized by their propagation step where the olefin monomer inserts into a carbon-transition metal link. ... 

By using a transition metal chloride catalyst and an iodine modified cocatalyst, ring-opening polymerization of C5 and C8 monocyclic olefins is controlled to prepare either cis polymers or trans products that are crystallizable. In copolymerization, the cis/trans units in the copolymers are regulated by adjusting the C5/C8 olefin monomer ratio. As the comonomer is increased, the copolymer becomes less crystalline and then completely amorphous at equal amounts of cis/trans units. Polymerization results are reported from WC16 and MoCl5 catalysts. 

Most ruthenium-initiated ROMP studies have been performed using (233) and strained cyclo-olefinic monomers such as norbornene688 and cyclobutenes,689 although several reports on the polymerization of 8-membered rings have also appeared.690-692 A wide range of functionalities are tolerated, including ethers, esters, amines, amides, alcohols, carboxylic acids, and ketones. 

Moreover, the molecular catalysts have provided systematic opportunities to study the mechanisms of the initiation, propagation, and termination steps of coordination polymerization and the mechanisms of stereospecific polymerization. This has significantly contributed to advances in the rational design of catalysts for the controlled (co)polymerization of olefinic monomers. Altogether, the development of high performance molecular catalysts has made a dramatic impact on polymer synthesis and catalysis chemistry. There is thus great interest in the development of new molecular catalysts for olefin polymerization with a view to achieving unique catalysis and distinctive polymer synthesis. 

It contains a weak dative auxilliary ligand that is readily replaced by incoming olefinic monomers (Fig. 8)... 

These catalysts represent the current state-of-the-art in ethylene copolymerization with polar olefinic monomers, being able to copolymerize a wide variety of polar monomers containing both O and N heteroatoms to generate completely linear, high molecular weight, random copolymers. There are leads to enhance the modest activity of these catalysts, and it will be interesting to watch further developments over the next few years. 

The catalytic transformation of olefins by transition metal complexes has received a great deal of attention during the past two decades. These catalytic reactions are important, especially industrially, because they represent some of the most economical ways to synthesize olefinic monomers or polymers. The more common types of these transformation reactions are (a) dimerization or polymerization of a-olefins (b) dimerization, oligomerization, cyclooligomerization, or polymerization of con-... 

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],... 

The problems (i)-(iii) are inextricably interrelated, because they all are, to some extent, of an analytical nature, and they have been solved satisfactorily only for relatively few systems. In particular, whether the propagating species are in fact ions, or whether they are highly polar covalent species, such as the esters of pseudo-cationic systems, has been clarified only for very few systems involving olefinic monomers although for many such our general background information on the chemistry of the species concerned and the pattern of the polymerisations themselves make an ionic propagating species much more likely [3, 4],... 

With the purpose of understanding the crosslinking mechanism of 1,2-polybutadiene with aromatic nitrene, we studied the reaction of phenylnitrene with unsaturated olefine monomers such as 3-methyl-1-butene and cyclohexene. These monomers are structually similar to a unit segment of 1,2-polybutadiene. 

Based on these results and the reaction mode of phenylazide with unsaturated olefine monomers as the model compound of the polymer, mechanisms [i] - [ill] are proposed for the crosslinking of 1,2-polybutadiene by bisazide. 

Mechanism [ill] represents crosslinking due to aziridine ring formation. This mechanism is supported by the decrease of ethylenic double bond of 1,2-polybutadiene and the fact that a large amount of aziridine compound is formed in the reaction of phenyl-nitrene with unsaturated olefine monomers, although the direct observation of it in 1,2-polybutadiene film matrix has not been accomplished in the present study. 

PBS (Figure 30) is an alternating copolymer of sulfur dioxide and 1-butene. It undergoes efficient main chain scission upon exposure to electron beam radiation to produce, as major scission products, sulfur dioxide and the olefin monomer. Exposure results first in scission of the main chain carbon-sulfur bond, followed by depolymerization of the radical (and cationic) fragments to an extent that is temperature dependent and results in evolution of the volatile monomers species. The mechanism of the radiochemical degradation of polyolefin sulfones has been the subject of detailed studies by O Donnell et. al. (.41). 

Cyclic olefin monomers such as indene, benzofuran, and so on, can give rise to two diisotactic polymers eiythro and threo, illustrated in the Fischer projection in 26 and 27, and to two different disyndiotactic polymers 28 and 29 (Scheme 5), as each monomeric unit is clearly defined and quite distinct from its neighbors (58, 61). For polymers of this type the terminology eiythro and threo is used also. 

Aliphatic polyketones are made from the reaction of olefin monomers and carbon monoxide using a variety of catalysts. Shell commercialized a terpolymer of carbon monoxide, ethylene, and a small amount of propylene in 1996 under the trade name Carilon (structure 4.79). They have a useful range between the Tg (15°C) and (200°C) that corresponds to the general useful range of temperatures for most industrial applications. The presence of polar groups causes the materials to be tough, with the starting materials readily available. 

The radiolysis of olefinic monomers results in the formation of cations, anions, and free radicals as described above. It is then possible for these species to initiate chain polymerizations. Whether a polymerization is initiated by the radicals, cations, or anions depends on the monomer and reaction conditions. Most radiation polymerizations are radical polymerizations, especially at higher temperatures where ionic species are not stable and dissociate to yield radicals. Radiolytic initiation can also be achieved using initiators, like those used in thermally initiated and photoinitiated polymerizations, which undergo decomposition on irradiation. 

Low- and high-density polyethylene, polypropene, and polymers of other alkene (olefin) monomers constitute the polyolefin family of polymers. All except LDPE are produced by coordination catalysts. Coordination catalysts are also used to produce linear low-density polyethylene (LLDPE), which is essentially equivalent to LDPE in structure, properties, and applications (Sec. 8-1 lc). The production figures given above for LDPE do not include LLDPE. The production of LLDPE now exceeds that of LDPE, with about 10 billion pounds produced in 2001 in the United States. (Copolymers constitute about one-quarter of all low density polyethylenes see Sec. 6-8b.)... 

Almost fitting on this list is methyl methacrylate (MMA), which polymerizes to PMMA with another methyl group attached to methyl acrylate. Another important olefin monomer is perfluoroethylene, which is ethylene, with the four Hs replaced by Fs, and it polymerizes to form Teflon. These monomers and polymers are ... 

R. Grubbs, C. Bielawski, and D. Benitez, Synthesis of macrocyclic polymers by ring insertion polymerization of cyclic olefin monomers, US Patent 6946533, assigned to California Institute of Technology (Pasadena, CA), September 20,2005. 

Acrylonitrile and other olefinic monomers can be grafted on polycaprolactam by an indirect method in which the polyamide powder is first submitted to nitro-sation with dinitrogen trioxide and then bulk polymerized at 60° C (12). 

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