Copolymer formation kinetics

Figure 6.8 (a) Morphology development of a PS/PMMA (60/40) non-reactive blend and a (PS+PS-OH)/ (PMMA + PMMA-r-NCO) reactive blend as a function of mixing time in an internal batch mixer (b) Copolymer formation kinetics in the reactive blend. After Hu and Kadri [31]... 

Why is the difference in copolymer formation kinetics between the three different rotation speeds not accompanied by a difference in the morphology development or the ultimate morphology There are two possible explanations. First of all, there is a much higher accuracy in quantifying the amount of the copolymer than the morphology. Secondly, for the three experiments, the copolymer surface coverage is always higher than a certain threshold. 

For a number of copolymers, whose kinetics of formation is described by nonideal models, the statistics of alternation of monomeric units in macromolecules cannot be characterized by a Markov chain however, it may be reduced to the extended Markov chain provided that units apart from their chemical nature... 

Crystallization from the melt often leads to a distinct (usually lamellar) structure, with a different periodicity from the melt. Crystallization from solution can lead to non-lamellar crystalline structures, although these may often be trapped non-equilibrium morphologies. In addition to the formation of extended or folded chains, crystallization may also lead to gross orientational changes of chains. For example, chain folding with stems parallel to the lamellar interface has been observed for block copolymers containing poly(ethylene), whilst tilted structures may be formed by other crystalline block copolymers. The kinetics of crystallization have been studied in some detail, and appear to be largely similar to the crystallization dynamics of homopolymers. 

Xie et al. (92, 93) synthesized simultaneous IPN from castor oil polyurethane and copolymers of vinyl monomers, including styrene, methyl methacrylate, and acrylonitrile, without cross-linker using a redox initiator at room temperature and both the formation kinetics of cross-linking and grafting on phase separation were examined. It was demonstrated that the resulting materials were mainly grafted IPN... 

A similar compartmentalization resulted in a successful one-pot process for the combination of ATRP and eROP, i.e., in a one-pot, two-step procedure (17). For this process CL, t-butyl methacrylate (t-BMA), Novozym 435 and 2 were heated to 60 °C to initiate the eROP and obtain the PCL block end-capped with 2. After 120 min. CuBr/dNbipy was added in order to activate the ATRP and thus the block copolymer formation. Figure 4 shows that during the first step of the consecutive process, i.e. the eROP, CL conversion reached 95 % while only negligible conversion of t-BMA was detected. Only upon addition of the ATRP catalyst, the radical polymerization started and reached ca. 43 % conversion within 180 min (300 min. total). Both reaction kinetics are comparable with the kinetics observed from the homopolymerization under similar conditions, suggesting that both reactions run undisturbed by each other (Figure 4). A clear... 

PA-6/PC Haake mixer at 280 °C/evidence for copolymer formation/reaction kinetics/ also blends including poly(propylene oxide) Costa and Oliveira 1998, 2002... 

Fredrickson and Milner [42] and O Shaughnessy et al. [43-48] developed theoretical approaches to the mechanism of interfacial reactions between reactive polymers. Accordingly, the kinetics of copolymer formation at the interface follows basically two time regimes (see also Figure 7.2) ... 

A successful reactive compatibilization requires that copolymer formation at the interfaces be perfectly controlled. To this end, three aspects should be taken into account chemistry used for the copolymer formation, molecular architecture of the copolymer, and kinetics of the reaction. 

The rate of copolymer formation between two immiscible reactive polymers depends on the interfacial area available for the reaction and the kinetics at the interfaces. For a given... 

Seminovych G M, Fainleib A M, Slinchenko E A, Brovko A A, Sergeeva L M and Dubkova V 1 (1999) Influence of carbon fibre on formation kinetics of cross-linked copolymer from bisphenol A dicyanate and epoxy oligomer. React Funct Polym 40 281-288... 

As will be shown later, the phase separation begins at very low degrees of conversion and is enhanced by increasing MM and voliune fraction of copolymer. The kinetics of IPN formation determines the onset of phase separation and influences strongly this process as a whole, whereas phase separation does not influence the kinetic cmves. This fact may serve as an additional confirmation of the assumption that the phase separation proceeds according to a spinodal mechanism, because in this case the compositions of two evolving phases are very close. 

The synthesis of N-silyl-phosphoranimines bearing mixed alkoxyalkoxy and trifluoroethoxy substituents is reported. The polymerization kinetics and the proposed anionic mechanism are also discussed. These monomers are utilized for the preparation of polyphosphazene random copolymers by the simultaneous polymerization of two phosphoranimines. Block copolymers have also been synthesized by addition of a second phosphoranimine after conversion of the first. Evidence for copolymer formation includes and 3lp NMR, SEC, solubility and DSC data. The differences between analogous random and block copolymers are discussed. 

Several studies have been performed to investigate the compatibalizing effect of blockcopolymers [67,158, 188,196-200], It is generally shown that the diblock copolymer concentration is enhanced at the interface between incompatible components when suitable materials are chosen. Micell formation and extremely slow kinetics make these studies difficult and specific non-equilibrium starting situations are sometimes used. Diblock copolymers are tethered to the interface and this aspect is reviewed in another article in this book [14]. 

Nomura and Fujita (12), Dougherty (13-14), and Storti et al. (12). Space does not permit a review of each of these papers. This paper presents the development of a more extensive model in terms of particle formation mechanism, copolymer kinetic mechanism, applicability to intervals I, II and III, and the capability to simulate batch, semibatch, or continuous stirred tank reactors (CSTR). Our aim has been to combine into a single coherent model the best aspects of previous models together with the coagulative nucleation theory of Feeney et al. (8-9) in order to enhance our understanding of... 

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