Mer unit

Condensation polymers are often formed from two distinct monomers, each of which is difunctional. The monomers have the forms AMA and BNB where A and B are functional groups that react to couple the M and N units and form a condensation by-product, AB. M and N are the mer units that form the polymer chain. The first step in the polymerization forms dimer ... 

This example of step-growth polymerization has two monomers that can react with each other but not with themselves. It has only one dimer that can be self-reactive. This pattern continues indefinitely with two trimers, one self-reactive tetramer, and so on. Molecules with an odd number of mer units will... 

Marvel, Dec, and Cooke [J. Am. Chem. Soc., 62 (3499), 1940] have used optical rotation measurements to study the kinetics of the polymerization of certain optically active vinyl esters. The change in rotation during the polymerization may be used to determine the reaction order and reaction rate constant. The specific rotation angle in dioxane solution is a linear combination of the contributions of the monomer and of the polymerized mer units. The optical rotation due to each mer unit in the polymer chain is independent of the chain length. The following values of the optical rotation were recorded as a function of time for the polymerization of d-s-butyl a-chloroacrylate... 

As previously reported ( ) linear poly(2,6-dichloro-l,4-phenyle-neoxide) exhibits the expected sharp singlet in its H-nmr spectrum, together with some minor peaks due to chemical asperities in the polymer. The spectrum of this polymer (Figure 3) is also very simple, consisting of the expected four sharp lines of the four inequivalent carbons in the mer unit 1. These same four lines may be identified Civ... 

In fact, six of the residual lines are exactly what one would expect for the 1,2-coupled mer unit 2. It was therefore concluded... 

The combined characterization results for all of the SAN samples (including the one polystyrene sample), i.e., weight fraction of AN mer units and [p] in... 

Further work on poly(arylene ether phenylimidazole)s led to a series of polymers containing two phenylimidazole units per mer unit (Eq. (5)) [24]. The dihydroxy monomers, 2,2 -(l,3- and l,4-phenylene)bis[(4-phenylhydroxy)-5-phenylimidazole] were prepared from the reaction of iso or terephthaldehyde, 4-hydroxybenzil and ammonium acetate in refluxing acetic acid. High molecular weight polymers as represented in Table 6 were readily prepared in DMAc. 

Fig. 4. Axial view of model of Structure II (5 mers). A pentamer model of either structure squats slightly because of the model s weight the helix of such a pentamer end tightens with the addition of subsequent mer units. Phenyl groups are more protruding...

Polymers, which received their name from Berzelius in 1833, are macromolecules which have many mer units or parts. Each mer unit (A) may have several functional groups but it is repeated n times to form the poisoner. 

Such a pol5mier has terminal groups T which can be the same or different than the mer unit, A. A polymer composed of several types of mer units, for example, A and B, is called a copolymer. Copolsmiers may be... 

Since most high molecular weight polymers do not mix on a molecular scale, it is desirable to determine compositional ranges of miscibility. The solubility of SAN copolymers with other polymers has been measured by a variety of techniques. The tendency of the materials to mix or phase separate is determined by the enthalpy of interactions between mer units in the polymers and by the molecular weight of the polymers. It was determined experimentally that... 

It is plausible to suppose that the temperature dependence should not be affected by branching unless the branching frequency is unusually high, since the friction factor f is presumed to reflect the behavior of relatively short (ca. five to twenty mer units) segments of the chain. Results on star-shaped branched polymers support this view 101, 136, 196). For example, the ratio exhibited the same dependence... 

In Fig. 7, the dynamics of a 400-mer united atom alkane under canonical MD and REPSWA canonical MD is compared. Since REPSWA MD has removed ALL 397 barriers it equilibrates quickly and easily. Standard MD remains stuck and its end to end distance does not reach the equilibrium value in Ins of simulation. The end to end distance under RESPSWA MD in... 

Polymer degradation can be described in terms of the weight of polymer, W, at time t, number of molecules, N, at time t, and DP as follows where m is the molecular weight of each mer unit. 

Picking an A group at random, we define the in direction from the chosen A toward the B group of the same mer unit. Out is then the opposite direction from the chosen A toward the remainder of the chain on the A side of the mer. Similar definitions apply to the in and out directions associated with B groups. 

Alternatively, M-w is obtained by picking an AB mer unit or an A group at random and then finding the expected weight of the molecule of which it is a part that is,... 

The mole fraction of polymer molecules consisting of x mer units will be given by the rate ratio... 

Dividing by Eq. (P6.44.15), one finally obtains the mole fraction of polymer of x mer units, that is. 

Resin IV has a lower specific gravity than does resin V (Table I), probably explained by the presence of two isopropylidene groups per mer unit. These reduce the ability of the polymeric chains to be as tightly packed as in resin V. The lower specific gravity of IV cannot be explained by the per cent crystallinity present in both polymers (Table I). If crystallinity were the major force, the specific gravity of resin IV would be higher. The remaining properties of resins IV and V listed in Table I exhibit little variation. 

There are many notations for representing block polymers. We have followed the most common in using A to represent a block of A mer units, with similar representation for B, C, etc., as shown in Table I. Here A-B represents a two block polymer, A-B-C a three block polymer, and A-B-A represents a three block polymer with A terminal blocks and B center blocks. (A-B)jj represents a linear multiblock polymer of alternating A and B blocks. 

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