Sequence Distribution in Copolymers

The procedure for obtaining expressions for the sequence distribution is similar to the calculating of molecular-weight distributions of polycondensates. In order to produce a sequence of N units of a monomer M, in the copolymer chain, N - 1 units must be added onto the growing end M. The probability of this sequence is (pi i) The sequence is terminated by an M2 unit. The probability for the addition of this unit to the Mj sequence is P12 = 1 — Pn- Thus, for the probability that a monomeric unit will occur in a sequence of N units, one has 

Equation (22-25) enables us to calculate the sequence distribution for a copolymer of given composition. The sequence distribution of a type of monomer thus depends only on the probability pn, and consequently, according to equation (22-4), only on the concentration of monomer and 

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Tosi, C. Sequence Distribution in Copolymers Numerical Tables. Vol. 5, pp. 451 —462. 

Tosi, C Sequence Distribution in Copolymers Numerical Tables. Vol. 5, pp. 451 to 462. Tsuchida, E. and Nishide, H. Polymer-Metal Complexes and Their Catalytic Activity. 

Monomer reactivity ratios and thus comonomer sequence distributions in copolymers can vary with copolymerization reaction conditions. The comonomer distribution could affect the geometry of the adsorbed polymer - mineral complex and the fines stabilization properties. 

Thermogravimetric analysis In thermogravimetric analysis (TGA) a sensitive balance is used to follow the weight change of the sample as a function of temperature. Its applications include the assessment of thermal stability and decomposition temperature, extent of cure in condensation polymers, composition and some information on sequence distribution in copolymers, and composition of filled polymers, among many others. 

The phenomenal growth in commercial production of polymers by anionic polymerization can be attributed to the unprecedented control the process provides over the polymer properties. This control is most extensive in organolithium initiated polymerizations and includes polymer composition, microstructure, molecular weight, molecular weight distribution, choice of functional end groups and even monomer sequence distribution in copolymers. Furthermore, a judicious choice of process conditions affords termination and transfer free polymerization which leads to very efficient methods of block polymer synthesis. 

Illustrative applications include the determination of stereochemical structure, and conformational preferences. 9 Another application is the determination of chemical composition and chemical sequence distributions in copolymers. A final example is the study of relaxation processes and molecular motions in general, including the determination of transition temperatures from changes in resonance line widths. 

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