SOLUTION COPOLYMERISATION

Compositionally uniform copolymers of tributyltin methacrylate (TBTM) and methyl methacrylate (MMA) are produced in a free running batch process by virtue of the monomer reactivity ratios for this combination of monomers (r (TBTM) = 0.96, r (MMA) = 1.0 at 80°C). Compositional ly homogeneous terpolymers were synthesised by keeping constant the instantaneous ratio of the three monomers in the reactor through the addition of the more reactive monomer (or monomers) at an appropriate rate. This procedure has been used by Guyot et al 6 in the preparation of butadiene-acrylonitrile emulsion copolymers and by Johnson et al (7) in the solution copolymerisation of styrene with methyl acrylate. 

I T-(isobutox.ymethyl)acrylamide (NIBa). MBA can be copolymer ised readily with many standard formulations, since it is scluble in most monomers. Reactivity ratios as determined in a benzene solution copolymerisation are ... 

Methyl methaciylate-maleic anltydiide eopoly mer matrices with different percentages of surface anhydride fuiKtional groups were prepared by solution copolymerisation. Acriflavine was botmd on the matrix surfaces by chemical bonding in organic medirrm. The amormt of acriflavine borrrrd to the rrratrix was spectroscopically characterised, arrd the in-vitro release rate of acriflavine in weakly basic medirrm was established along with the determination of its antirrricrobial activity. 9 refs. 

Figure 5.7 The reactor-distributor and method of continuous solution copolymerisation. 1 - polymeriser 2 - drive of the mixing device 3 - connection pipe for the introduction of the gas-liquid mixture 4, 5 - connection pipe for the separate introduction of the catalj ic complex components 6 - connection pipe for taking off the copolymer 7 - manifold 8, 9,12 - tubular turbulent divergent-convergent reactors 10 - tubular turbulent reactor-distributor and 11- distributing pipes...

The flow sheet of a continuous solution copolymerisation of ethylene and propylene (Figure 5.10) has been proposed. Here, tubular turbulent reactors are used at the following stages [8, 9, 12] 1) preparation of the homogeneous gas-liquid mixture and its introduction to the polymerisers working in parallel 2) formation of macromolecule growth centres and 3) decomposition of the catalyst with water and the introduction of the stabiliser to the polymer. 

The experimental values of V- and M-centred triads from [ H] triads were compared with the theoretical values from Harwood s [171] statistical model using copolymerisation reactivity ratios. The reactivity ratios for free-radical solution copolymerisation of V with M were calculated using the Kelen-Tudos (KT) [172] and the nonlinear error in variables (EVM) [173] methods using the RREVM [174] program. Homonuclear H-2D-COSY and 2D-NOESY NMR of the copolymer sample were recorded for determining the interactions between different protons in the copolymer chain. 

Fourier transform IR spectroscopy and IH NMR spectroscopy. The crosslinking ability is verified by the formation of an insoluble gel of the macromonomer in solution homopolymerisations and also in solution copolymerisations with a primary monomer, n-butyl methacrylate in the presence of 2,2 -azobis(isobutyro-nitrile) (AIBN) at 700 deg.C. 17 refs. 

As a rule, LLDPE resins do not contain long-chain branches. However, some copolymers produced with metallocene catalysts in solution processes can contain about 0.002 long-chain branches per 100 ethylene units (1). These branches are formed in auto-copolymerisation reactions of ethylene with polymer molecules containing vinyl double bonds on their ends (2). 

Dow catalysts have a high capabihty to copolymetize linear a-olefias with ethylene. As a result, when these catalysts are used in solution-type polymerisation reactions, they also copolymerise ethylene with polymer molecules containing vinyl double bonds at their ends. This autocopolymerisation reaction is able to produce LLDPE molecules with long-chain branches that exhibit some beneficial processing properties (1,2,38,39). Distinct from other catalyst systems, Dow catalysts can also copolymerise ethylene with styrene and hindered olefins (40). 

A variety of ionomers have been described in the research literature, including copolymers of a) styrene with acrylic acid, b) ethyl acrylate with methacrylic acid, and (c) ethylene with methacrylic acid. A relatively recent development has been that of fluorinated sulfonate ionomers known as Nafions, a trade name of the Du Pont company. These ionomers have the general structure illustrated (10.1) and are used commercially as membranes. These ionomers are made by copolymerisation of the hydrocarbon or fluorocarbon monomers with minor amounts of the appropriate acid or ester. Copolymerisation is followed by either neutralisation or hydrolysis with a base, a process that may be carried out either in solution or in the melt. 

The use of copolymers is essentially a new concept free from low-MW additives. However, a random copolymer, which includes additive functions in the chain, usually results in a relatively costly solution yet industrial examples have been reported (Borealis, Union Carbide). Locking a flame-retardant function into the polymer backbone prevents migration. Organophosphorous functionalities have been incorporated in polyamide backbones to modify thermal behaviour [56]. The materials have potential for use as fire-retardant materials and as high-MW fire-retardant additives for commercially available polymers. The current drive for incorporation of FR functionality within a given polymer, either by blending or copolymerisation, reduces the risk of evolution of toxic species within the smoke of burning materials [57]. Also, a UVA moiety has been introduced in the polymer backbone as one of the co-monomers (e.g. 2,4-dihydroxybenzophenone-formaldehyde resin, DHBF). 

Most copolymers are heterogeneous in both molecular weight and composition. The latter of these arises from the mechanism of the copolymerisation (particularly at high conversion) and individual copolymer molecules differ slightly in their value of WA. Solutions of heterogeneous copolymers constitute multicomponent systems... 

The inclusion of mineral acid in the grafting solution has recently been shown to increase the radiation copolymerisation yield, particularly when styrene is grafted to trunk polymers like wool (3) and cellulose (4) i.e. polymers which readily swell in polar solvents such as methanol. This acid effect is important since for many copolymerisation reactions, relatively low radiation doses are required to yield finite graft. The process is particularly valuable for monomers and/or polymers that are either radiation sensitive or require high doses of radiation to achieve the required graft. 

Efficient copolymerisation can also be achieved in solvents other than the alcohols (Table VI). Thus the order of effectiveness for the present copolymerisation of these additional solvents is DMSO>DMF>dioxan>acetone>>chloroform>hexane. Acid enhancement is also observed in the first of these four solvents (Table VI). Characteristically (5), acid increases the intensity of the Tromms-dorff peak if it is already present in the system (dioxan) or alternatively induces the formation of the gel peak if it is not present in the solutions prior to acid addition (DMSO). 

Working with a solution is needed for polymers which above their melting point would degrade (example aromatic polyamide fibres such as Kevlar and Twaron). For fibres the removal of the solvent is not too problematic. In e.g. injection moulding applications solvents caimot be used here thermotropic LCP s have to be used. Since these would degrade during processing, they are diluted by copolymerisation (example poly-hydroxy-benzoic acid - co - PETP)... 

PolyHIPE materials have also been prepared by polycondensation in high internal phase emulsions [153]. Thus, a resorcinol-formaldehyde (RF) porous copolymer was synthesised from an o/w HIPE of cyclohexane in an aqueous solution of resorcinol, formaldehyde and surfactant. Addition of an acid catalyst to the emulsion, followed by heating, resulted in copolymerisation. Other systems prepared included urea-formaldehyde, phenol-formaldehyde, melamine-formaldehyde and a polysiloxane-based elastomeric species. 

This method involves graft copolymerisation using redox initiators [70] or free radical initiators [71, 72, 73] usually in the solution phase, occasionally under the influence of temperature, predominantly in the latter case. Redox systems have extensively been used to generate active sites especially on the natural polymers [74] (like cellulose). Transition metals viz. Cr+6, V+5, Ce+4,... 

NMR spectroscopy. On the other hand it was found that T2 of the solute in the rubber cured in the presence of triallyl cyanurate (TAC) increased on curing, despite the equilibrium swelling ratio decreasing. This surprising result was explained by a change in the polymer-solvent interactions on copolymerisation with TAC. 

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