Functionalization of Monomer

The approach of synthesizing a monomer containing the desired functional group followed by (co)polymerization can be illustrated for the poly[4(5)-vinylimidazole] catalyst (VII) described in Sec. 9-lj. Synthesis involves the sequence of reactions starting from histidine (XXXVII) to yield 4(5)-vinylimidazole (XXXVIII), which is subsequently polymerized by radical initiation [Overberger and Vorchheimer, 1963], 

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Fig. 1. Copolymer composition as a function of monomer feed ratio for various reactivity ratio combiaations, designated I—V and explained ia the text...

Fig. 3. Elastomer properties as a function of monomer composition, butyl acrylate (BA), ethyl acrylate (FA), and methoxyethyl acrylate (MEA). (a), (—) glass-transition temperature (------------) swelling in ASTM No. 3 oil (b) (-) residual elongation at break, %, after heat aging.

Figure 3.3 Cumulative ( ) and instantaneous ( ) initiator efficiency (/) of AIBN as initiator in S polymerization (50% v/v toluene, 70 °C) as a function of monomer conversion (lines are a polynomial fit to the datapoints).1,32...

Fig. 5. GPC curves of PIB prepared with r-BuCl/Et2AlCl/Mea at -60° as a function of monomer concentration...

In general, for polymerization reactions, the heat generation rate is not a single-valued function of temperature, g(t), but also a function of monomer and catalyst concentrations, f(c). This is particularly important in high conversion reactions where a certain amount of peaking can be tolerated. 

The rate constants in the reactions (29) may be conveniently envisaged as elements of symmetric matrix k. In order to calculate the statistical characteristics of a particular polycondensation process along with matrix k parameters should be specified which characterize the functionality of monomers and their stoichiometry. To this end it is necessary to indicate the matrix f whose element fia equals the number of groups A in an a-th type monomer as well as the vector v with components Vj,... va,..., v which are equal to molar fractions of monomers M1,...,Ma,...,M in the initial mixture. The general theory of polycondensation described by the ideal model was developed more than twenty years ago [2]. Below the key results of this theory are presented. 

In the absence of adsorption, inclusion, or exclusion, a polymer is fractionated on a GPC column according to the hydrodynamic volume.40138 The hydrodynamic volume is a function of monomer identity, as well as polymer molecular weight, branching, and cross-linking. The polymer chains in any given chromatographic fraction have roughly the same hydrodynamic volume. 

Figure 31 Copolymer composition as a function of monomer mixture composition in the case of styrene methyl methacrylate mixtures. Reproduced from Mercier and Marechal [15], Reproduit avec I autorisation de I editeur. Tous droits reserves.

Figure 5. Mn and N as functions of monomer input WIBve in n-heptane at —70°C. [p-DCC]0 is 0.50 mM [AgSbFs]0 is 1.1 mM. 1BVE addition rates (g/min) are 0.38 (9), 0.57 (O), 0.78 (9). The dashed lines show the data obtained in CHtCU under the same conditions.

Figure 1. Lower critical solution temperatures of copolymers of N-isopropyl acrylamide with other N-alkyl acrylamides as a function of monomer input ratios.

Figure 5. Lower Critical Solution Temperatures of Copolymers of N-isopropyl Acrylamide and N-n- and N-t-butyl Acrylamide as a Function of Monomer Input Ratios.

Multiplication by [M2] gives what are generally referred to as the copolymerization equations, Equations 7.17 and 7.19, which gives the copolymer composition without the need to know any free radical concentration, and which gives the composition of the growing polymer as a function of monomer feed (Equation 7.19). 

FIGURE 7.1 Instantaneous copol5uner composition as a function of monomer composition and initiator employed for the comonomer system of styrene and methyl methacrylate using different modes of initiation. (Adapted from handler, Y., Comptes Rendus, 230, 539, 1950. With permission.)... 

The functionalization of polymer approach is used much more often than the functionalization of monomer approach at present because functional polymers such as chloro-methylated polystyrene are readily available with different porosities and degrees of chloromethylation. There are relatively few situations where less work is needed to use the functionalization of monomer approach. Also, many practitioners of polymer reagents,... 

Figure 6. Mole percent methyl methacrylate incorporated in poly(methyl)meth-acrylate-co-3-oximino-2-butanone methacrylate) copolymers as a function of monomer feed composition determined by Raman spectroscopy. Key -----------ideality...

Fig. 8. Calculated and experimental rates of polymer deposition as a function of monomer flow rate [after Tibbitt et al. >]...

The mixture CMC is plotted as a function of monomer composition in Figure 1 for an ideal system. Equation 1 can be seen to provide an excellent description of the mixture CMC (equal to Cm for this case). Ideal solution theory as described here has been widely used for ideal surfactant systems (4.6—18). Equation 2 can be used to predict the micellar surfactant composition at any monomer surfactant composition, as illustrated in Figure 2. This relation has been experimentally confirmed (ISIS) As seen in Figure 2, for an ideal system, if the ratio XA/yA < 1 at any composition, it will be so over the entire composition range. In classical phase equilibrium thermodynamic terms, the distribution coefficient between the micellar and monomer phases is independent of composition. 

The predicted adsorption isotherms From ideal solution theory (Equations 6—9) are also shown in Figures 3—5. Since it is diFFicult to see degree oF Fit on a log-log plot, the ability to describe the data is better illustrated in Figures 6-9, where the CACm is plotted For several adsorption levels as a Function oF monomer composition along with predictions From Equation 6. 

As mentioned in Chapter 2, if two comonomers are not connected with the template by covalent bonds, reactivity ratios can be calculated on the basis similar to the conventional copolymerization. The only difference is that reactivity ratios ri and T2 for both monomers depend on the concentration of the template. In order to compare experimental data with these considerations, copolymerization of methacrylic acid with styrene was carried out in the presence of PEG (mol. wt. 20,000) as the template. The reactivity ratios rf and r2 can be calculated according to the Kellen-Tiidos method. The results are shown in the Figure 5.4. According to this method, a proper functions of monomer mixture composition, R, and copolymer composition, E, were plotted ... 

Fig. 4. Rate of cationic polymerization of tetrahydrofuran to polyether at 0° C as function of monomer concentration. Reproduced, with permission, from Vofsi and Tobolsky J. Polymer ScL 3 A, 3261 (1965).

S - SB BS- SB BS SB BS - SB B and so forth. Hence, one can produce a whole spectrum of products all identical in respect to their composition and molecular weights but differing in the distribution of the monomer units along the chain. Their properties as a function of monomer distribution may then be investigated. 

A step-growth polymerization (with or without elimination of low-molar-mass products) involves a series of monomer + monomer, monomer + oligomer, monomer or oligomer + macromolecule, and macromolecule + macromolecule reactions. The molar mass of the product grows gradually and the molar mass distribution becomes continuously wider. Functionalities of monomers and the molar ratio between coreactive sites are the main parameters for controlling the polymer structure. 

Fig. 16 Intramolecular composition profile presented as a function of monomer number i/N for hydrophobic/amphiphilic copolymer chains obtained via emulsion copolymerization, at a few chain lengths N indicated near the curves. Adapted from [25]...

Carbon-13 nuclear magnetic resonance was used to determine the molecular structure of four copolymers of vinyl chloride and vinylidene chloride. The spectra were used to determine both monomer composition and sequence distribution. Good agreement was found between the chlorine analysis determined from wet analysis and the chlorine analysis determined by the C nmr method. The number average sequence length for vinylidene chloride measured from the spectra fit first order Markovian statistics rather than Bernoullian. The chemical shifts in these copolymers as well as their changes in areas as a function of monomer composition enable these copolymers to serve as model... 

Contrary to viscosity measurements GPC provides number average molar mass data (Mn). For a few studies on the polymerization of BD with Nd-carboxylate-based catalyst systems GPC was systematically applied for the monitoring of Mn as a function of monomer conversion. In these studies three catalyst systems were used (1) NdV/DIBAH/EASC [178], (2) NdV/TIBA/EASC [179] and (3) NdO/TIBA/DEAC [188]. In the first two studies linear Mn-conversion plots were obtained at various molar ratios Al/ Ndv- In these studies, however, molar mass data at low monomer conversions (<20%) are lacking and positive intercepts on the Mn-axis were found. For the ternary catalyst system NdO/TIBA/DEAC used in the third of these studies the concentrations of Nd and TIBA were varied. A linear increase of Mw and Mn on monomer conversion was found. Deviations from linearity were also observed for low monomer conversions. 

Fig. 7. Activity retention as a function of monomer concentration in the immobilized enzymes by radiation polymerization method. Enzyme a-amylase(— 24 °C, 1 x 106 rad) glucose isomer-ase (—45°C, 1 x 106 rad) O a-glucosidase (—78°C, 1 x 106 rad) A glucoamylase (—78CC, 1 x 106 rad). Monomer HEMA (2-hydroxyethyl methacrylate)...

The mechanism can be best understood within the framework of the conventional theory of radical chain kinetics, provided that certain of the usual simplifying assumptions are omitted. A solution is given to the problem of steady-state polymerization rate as a function of monomer and initiator concentration, taking into account termination reactions of primary radicals and recombination of geminate chains arising from the same initiation event. This model is shown to account for the kinetic data reported herein. With appropriate rate constants it should be generally applicable to radical polymerizations. 

Figure 2. Relative rate of copolymerization of styrene (Mj) and a-methylstyrene (M2) at 60°C. as a function of monomer composition (12)...

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