Anionic polymerisation of styrene

Thermal explosion which occurred during fast anionic polymerisation of styrene, catalysed by butyllithium, was prevented by addition of low MW polystyrene before the catalyst. 

It is possible to produce a block copolymer by the anionic polymerisation of styrene and butadiene as depicted below. The polystyrene and polybutadiene are mutually incompatible and hence phase separate to give the morphology also depicted below ... 

Polystyrene was prepared by the anionic polymerisation of styrene in toluene plus THF mixtures (4 1 volume ratio) using n-butyl lithium as initiator. After removing a sample for analysis at this stage, the remainder of the living polystyrene was reacted with a five molar excess of trichloromethylsilane for 15 min and then excess methanol introduced. The methoxy-terminated polystyrene was freeze-dried from dioxan. The method described here essentially follows the route proposed by Laible and Hamann (6). 

In conclusion, the reality of helical growth, which was proposed by Lundberg and Doty, seems to be proved beyond any doubt. In fact, these phenomena may play an important role in other polymerising systems. Szwarc (91) suggested that the results of Williams et al. (92), who studied anionic polymerisation of styrene in different solvents, may be explained in terms of a helical growth, and a similar suggestion was made by Ham (93) to account for peculiarities some radical polymerisations.Well-documented studies of anionic polymerisation of methyl methacrylate (94) lead to the conclusion that random-coiled polymers, as well as helices, may participate in this reaction. This subject has been fully reviewed in a recent publication (95). 

Stretch, C., and G. Allen Anionic polymerisation of styrene. Proc. Chem. Soc. (London), p. 399. 

The influence of reciprocal miscibility between the methacrylic copolymer containing cyclic anhydride groups and the styrenic oligomers was investigated in the case of monohydroxylated oligomers, which were also prepared by anionic polymerisation of styrene and further deactivation with ethyleneoxide. 

An example of the grafting from strategy is a treatment of SWNTs with sec-butyllithium that generates carbanions on the nanotube surface. These carbanions can serve as initiators of anionic polymerisation of styrene for in situ preparation of polystyrene-grafted tubes. This procedure allows the debundling of SWNTs and the production of a homogeneous dispersion of nanotubes in polystyrene solution. 

The time-dependent evolution of the polymerisation and copolymerisation reactions of styrene/unsaturated polyester resin was characterised using optical levitation with Raman spectroscopy (135). The n-butyllithium-initiated anionic polymerisation of styrene in ethylbenzene was measured using Raman spectroscopy (214). 

No. 16,1996, p.3665-73 ANIONIC POLYMERISATION OF STYRENE AND BUTADIENE INITIATED BYN-BUTYLLITHIUM IN ETHYLBENZENE DETERMINATION OF THE PROPAGATION RATE CONSTANTS USING RAMAN SPECTROSCOPY AND GEL PERMEATION CHROMATOGRAPHY... 

Scheme 10.4 Living anionic polymerisation of styrene and isoprene...

It is possible to illustrate the kinetics of anionic polymerisation by the polymerisation of styrene with potassium amide in liquid ammonia. The first step involves the bread-down of initiators into ions. 

Recent examples of the application of three-dimensional H/13C/Y correlation spectroscopy for the characterisation of polymers included studies of polystyrene samples obtained by diphenylphosphinyl radical initiated polymerisation of styrene (Y = 31P),38,39,86 and the characterisation of Sn-containing polybutadiene that was prepared by anionic polymerisation... 

The detrimental effect of tetrabutylammonium iodide and tetrafluoroborate on the rate of polymerisation of styrene in the presence of acetyl perchlorate can easily be ex-plaiited by an anion-exchange reaction with the propagating esta to give a much less active chain carrier. 

Higginson, W.C.E., Wooding, N.S., 1952. Anionic polymerisation 1. The polymerisation of styrene in liquid ammonia solution catalysed by potassium amide. J. Chem. Soc. 760-774. 

The cure mechanism for curing triglycidyl -amino phenol with diaminodiphenylsulfone was studied. The concentration of primary and secondary amine and epoxide groups were monitored directly as a function of cure with NIR spectroscopy. In similar fashion, monitoring of the percent conversion of methyl methacrylate to PMMA in situ in a mould used short-wavelength NIR spectroscopy. NIR spectroscopy was also used to monitor conversion during conventional, anionic solution polymerisation of styrene and isoprene to homopolymers and block copolymers (314). 

Near-IR spectroscopy (10000-4000/cm) was successfully used to monitor conversion dining conventional, anionic solution polymerisation of styrene and isoprene to homopolymers and block copolymers. The conversion of the vinyl protons in the monomer to methylene protons in the polymer was easily monitored under conventional (10-20% solids) solution polymerisation conditions. In addition to the need for an inert probe, high sampling frequencies were required since polymerisation times ranged from 5s in tetrahydrofuran to 20 minutes in cyclohexane. Preliminary data indicate that near IR is capable of detecting sequence distribution for tapered block copolymers, geometric isomer content, and reactivity ratios for free-radical copolymerisation. 20 refs. USA... 

The polymerisation of styrene in miniemnlsions stabilised with anionic sodium dodecyl sulphate or nonionic Lntensol AT50 results in stable polymer dispersions with particle diameters between 30 and 480 nm and narrow particle size distributions. Steady-state mini-emulsification results in a system with critical stability , i.e. the droplet size is the prodnct of a rate equation of fission by ultrasound and fusion by collisions, and the mini-droplets are as small as possible for the timescales involved. The droplet growth by monomer exchange, or the T1 mechanism, is effectively suppressed by addition of a very hydrophobic material, whereas droplet growth by collisions, or the T2 mechanism, is subject to the critical conditions. The growth of the critically stabilised miniemulsion droplets is usually slower than the polymerisation time therefore, in ideal cases, a 1 1 copy of droplets to particles is obtained, and the critically stabilised state is frozen. 6 refs. 

EMULSION POLYMERISATION OF STYRENE STABILISED BY MIXED ANIONIC AND NONIONIC SURFACTANTS Chem C S Lin S Y Chen L J Wn S C Taiwan,National Institnte of Technology Taiwan,National University... 

When styrene is polymerised, polyst5rene is formed. The polymerisation of styrene is a chain growth reaction and it is induced by any known initiation techniques such as heat, free radical, anionic or cationic addition. The product polystyrene is a white polymer with high clarity and good physical and electrical properties. 

By the same method of living radical polymerisation, a series of block copolymers of poly(ethylene oxide-styrene) with narrow polydispersity were synthesised by the following two-step approach [96]. Initially, living anionic polymerisation of ethylene oxide with sodium-4-oxy-2,2,6,6-tetramethyl-l-piperidinoxyl as initiator yields polyethylene oxide with ARs at the chain end ... 

The requirements for a polymerisation to be truly living are that the propagating chain ends must not terminate during polymerisation. If the initiation, propagation, and termination steps are sequential, ie, all of the chains are initiated and then propagate at the same time without any termination, then monodisperse (ie, = 1.0) polymer is produced. In general, anionic polymerisation is the only mechanism that yields truly living styrene... 

In the absence of impurities there is frequently no termination step in anionic polymerisations. Hence the monomer will continue to grow until all the monomer is consumed. Under certain conditions addition of further monomer, even after an interval of several weeks, will eause the dormant polymerisation process to proceed. The process is known as living polymerisation and the products as living polymers. Of particular interest is the fact that the follow-up monomer may be of a different species and this enables block copolymers to be produced. This technique is important with certain types of thermoplastic elastomer and some rather specialised styrene-based plastics. 

The styrene-diene triblocks, the main subject of this section, are made by sequential anionic polymerisation (see Chapter 2). In a typical system cc-butyl-lithium is used to initiate styrene polymerisation in a solvent such as cyclohexane. This is a specific reaction of the type... 

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