Polymerization of aromatic monomer

Title Modified Suzuki-Method for Polymerization of Aromatic Monomers... 

Incorporation of monomers with similar characteristics to the hydrophobic tails of the surfactants involved (typically alkane chains of DODAB and DMPC) tends to suppress phase separation somewhat, and results in either multi-polymer bead aggregates (e.g., necklaces) or parachutes containing an elliptical rather than a spherical latex bead. Copolymerization of butyl methacrylate with ethylene glycol dimethacrylate in DODAB vesicles resulted in polymer necklaces where the polymer beads appear randomly dispersed in the vesicle bilayer [15] in contrast to the polymer shells observed by Hotz and Meier [10] for the same reaction in DODAC vesicles. Similarly, polymerization of octadecylacry-late, another straight-chain monomer, in DODAB vesicles produced parachutes with extremely elHpsoidal polymer beads in contrast to the rather spherical beads observed commonly for the polymerization of aromatic monomers such as styrene in DODAB [12]. Presumably these differences are caused by an increased compatibility between the surfactant bilayer and the monomer chosen. 

The conversion of aromatic monomers relative to C-5—C-6 linear diolefins and olefins in cationic polymerizations may not be proportional to the feedblend composition, resulting in higher resin aromaticity as determined by nmr and ir measurements (43). This can be attributed to the differing reactivity ratios of aromatic and aHphatic monomers under specific Lewis acid catalysis. Intentional blocking of hydrocarbon resins into aromatic and aHphatic regions may be accomplished by sequential cationic polymerization employing multiple reactors and standard polymerization conditions (45). 

In order to increase the solubiUty parameter of CPD-based resins, vinyl aromatic compounds, as well as other polar monomers, have been copolymerized with CPD. Indene and styrene are two common aromatic streams used to modify cyclodiene-based resins. They may be used as pure monomers or contained in aromatic steam cracked petroleum fractions. Addition of indene at the expense of DCPD in a thermal polymerization has been found to lower the yield and softening point of the resin (55). CompatibiUty of a resin with ethylene—vinyl acetate (EVA) copolymers, which are used in hot melt adhesive appHcations, may be improved by the copolymerization of aromatic monomers with CPD. As with other thermally polymerized CPD-based resins, aromatic modified thermal resins may be hydrogenated. 

Styrene [100-42-5] (phenylethene, viaylben2ene, phenylethylene, styrol, cinnamene), CgH5CH=CH2, is the simplest and by far the most important member of a series of aromatic monomers. Also known commercially as styrene monomer (SM), styrene is produced in large quantities for polymerization. It is a versatile monomer extensively used for the manufacture of plastics, including crystalline polystyrene, mbber-modifted impact polystyrene, expandable polystyrene, acrylonitrile—butadiene—styrene copolymer (ABS), styrene—acrylonitrile resins (SAN), styrene—butadiene latex, styrene—butadiene mbber (qv) (SBR), and unsaturated polyester resins (see Acrylonithile polya rs Styrene plastics). 

Organic peroxide-aromatic tertiary amine system is a well-known organic redox system 1]. The typical examples are benzoyl peroxide(BPO)-N,N-dimethylani-line(DMA) and BPO-DMT(N,N-dimethyl-p-toluidine) systems. The binary initiation system has been used in vinyl polymerization in dental acrylic resins and composite resins [2] and in bone cement [3]. Many papers have reported the initiation reaction of these systems for several decades, but the initiation mechanism is still not unified and in controversy [4,5]. Another kind of organic redox system consists of organic hydroperoxide and an aromatic tertiary amine system such as cumene hydroperoxide(CHP)-DMT is used in anaerobic adhesives [6]. Much less attention has been paid to this redox system and its initiation mechanism. A water-soluble peroxide such as persulfate and amine systems have been used in industrial aqueous solution and emulsion polymerization [7-10], yet the initiation mechanism has not been proposed in detail until recently [5]. In order to clarify the structural effect of peroxides and amines including functional monomers containing an amino group, a polymerizable amine, on the redox-initiated polymerization of vinyl monomers and its initiation mechanism, a series of studies have been carried out in our laboratory. 

Later on, Ballard et al. [42, 43] developed an improved precursor route starting from 5,6-diacetoxycyclohexa-1,3-diene (18), the so-called 1C1 route. The soluble precursor polymer 19 is finally aromatized thermally into PPP 1 via elimination of two molecules of acetic acid per structural unit. Unfortunately, the polymerization of the monomer does not proceed as a uniform 1,4-polymerization in addition to the regular 1,4-linkages ca. 10% of 1,2-linkages are also formed as result of a 1,2-polymerization of the monomer. 

Bfx, Fx, and related compoimds are the subject of a great munber of invention patents especially related to its uses in material sciences. For example, they were included in the formiflation as rubber additives [245,246], as inhibitors in the polymerization of aromatic vinyl monomers [247], as components in the igniting composition for inflation of airbags [248,249], as explosives [250-253], as soHd propellants [254], as burn-rate modifiers [255], and as liquid-crystalHne materials [256]. 

The time-course of deposition of aromatic monomers into the polymer laid down by suberizing tissue slices indicates that the phenolic matrix is deposited simultaneously with or slightly before the aliphatic components. The specific anionic peroxidase appeared with a time-course consistent with its involvement in the polymerization and deposition of the phenolic matrix of the suberin. Increase or decrease in suberin content involves similar changes in both the aliphatic and aromatic components and such changes are associated with the expected increase or decrease in the anionic peroxidase activity caused by physical or biological stress. 

The anionic graft polymerization of vinyl monomers onto carbon fiber or graphite powder initiated by metalized carbon fiber has been investigated. The metalation of polycondensed aromatic rings of a carbon fiber surface was achieved by treatment of the carbon fiber with BuLi in Ar,Ar,Ar, AT -tetramethylethylenediamine. The anionic polymerization of methylmethacrylate and styrene was reported. No grafting was observed when carbon fiber was treated simply with BuLi in THF or toluene [44,45]. 

Hyperbranched polymers are formed by polymerization of AB,-monomers as first theoretically discussed by Flory. A wide variety of hyperbranched polymer structures such as aromatic polyethers and polyesters, aliphatic polyesters. polyphenylenes, and aromatic polyamides have been described in the literature. The structure of hyperbranched polymers allows some defects, i.e. the degree of branching (DB) is less than one. The synthesis of hyperbranched polymers can often be simplified compared to the one of dendrimers since it is not necessary to use protection/deprotection steps. The most common synthetic route follows a one-pot procedure " where AB,-monomers are condensated in the presence of a catalyst. Another method using a core molecule and an AB,-monomer has been described. ... 

Polycarbonates, both aliphatic and aromatic, have been prepared by the ring opening polymerization of cyclic monomers or oligomers [22], Cyclic monomeric precursors are more common in aliphatic polycarbonates, but because of steric reasons aromatic polycarbonates can only be prepared from cyclic oligomers. Both cationic and anionic initiators have been examined and anionic initiators appear to be more efficient. 

The polymerization of compounds having active methyne groups has also been reported [81] (Eq. 8). The oxidative coupling polymerization of these monomers follows a mechanism similar to that of phenols. The catalytic cycle observed in the polymerization of / -phcnylcncdiaminc with Fe(edta) as the catalyst in an aqueous solution differs from that in the polymerization of phenols as follows The activation of monomers usually involves either electron transfer from the anion or elimination of a hydrogen atom from the monomer. The oxidative polymerization of phenols uses the former mechanism of the electron transfer. In contrast, in the case of the polymerization of aromatic diamines as monomers, the neutral amines are coordinated to the catalyst, followed by the subsequent electron transfer and dehydronation. The dehydronation proceeds by the reaction with 02. Another mechanism has also been proposed where dehydrogenation... 

Mechanism. The ability of S02 to participate in complex formation with unsaturated hydrocarbons and a host of other compounds such as amines, ethers, phenols, and aromatic hydrocarbons is known (2, 6, 11, 22). SO has been found to initiate polymerization of some monomers... 

The polymerizations proceeded at 25° C except 4,4 -bis(l-naph-thyl)biphenyl. In this case the monomer had insufficient solubility at room temperature. The polymerization of this monomer at 80° C resulted in the formation of significant amounts (26-78%) of CHCl3-insoluble fractions. The highest molecular weight was obtained with 337 M = 4000 MJ Mn = 2.5 DP = 10). Thus this polymer has 40 aromatic rings in each polymer chain. 

Retarders and inhibitors differ only in the frequency with which propagating radicals react with them rather than with monomer and possibly also in the ability of the radicals resulting from such reactions to reinitiate. It is lo be expected, then, that a compound may not exert the same elTect in the polymerization of different monomers. For example, aromatic nitro compounds that are inhibitors in vinyl acetate polymerizations are classified as retarders in polystyrene syntheses. 

Bifunctional Initiation. The bifunctional initiators like alkali metal complexes of polycyclic aromatic compounds can be used to produce ABA triblock copolymers even when the A anion is not sufficiently basic to initiate polymerization of B monomers. In these cases polymerization would be started with monomer B to produce a polymeric dianion which could initiate polymerization of the A monomer which is added later. These initiators can be prepared only in aliphatic ethers, however. This precludes their use for the synthesis of useful styrene-diene ABA copolymers because polydienes made anionically in such solvents have low 1,4 contents and are not good rubbers. 

In the photopolymerization of methacrylamide by benzoin methyl ether, chain-transfer to monomer has been found to be important, and benzalde-hyde is reported to be an inefficient photoinitiator of methyl methacrylate polymerization unless benzophenone and triethylamine are present. Acetophenone has been found to sensitize the cycloaddition of maleic anhydride to 7-oxabicyclo[2.2.1]heptan-5-one-2,3-dicarboxylic anhydride, , a-hydroxy-acetophenone derivatives have been found to be non-yellowing initiators, and h.p.l.c. has been used to determine residual carbonyl photoinitiators in u.v.-cured resins. In the emulsion-polymerization of methyl methacrylate using an aromatic ketone and a continuous or intermittent laser, the former conditions were found to be similar to those under continuous u.v. irradiation. The dependence of the polymerization rate and average chain-length on the absorbance of the initiator used in the photoinitiated polymerization of vinyl monomers has been studied. Interestingly, irrespective of all conditions, maximum conversion is observed when initiator absorbance is 2.51. "... 

Usually, photoinitiating systems based on aromatic ketone/tertiary amine combinations are more active in the polymerization of unsaturated monomers compared with ketones alone [37], particularly in the air, not only because the formation of exciplexes competes efficiently with the quenching of ketone triplet state by oxygen, but also because amines behave as oxygen scavengers through a chain process [34] (Scheme 8) ... 

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