Polyamides, chain type

Moments of rank 1 -4 formed from the components x,y, and z of the chain vector r and expressed in the coordinate system affixed to the first unit are calculated as functions of chain length n for p-phenylene polyamides of type I, -(NH-CGH4-C0)n-, of type II, -(NH-Cgfy—NH—CO—C6H4—C0)n/2-, and of the corresponding polyesters. 

Block copolymers are also formed by condensation of two chain types with functional end groups. Some kinds of polyurethanes are examples. Dissimilar and mutually immiscible polymers can be connected in this way. Henderson and Szwarc condensed a, co-polystyrenedicarboxylic acid with a polyamide carrying terminal amino groups [272], producing the copolymer poly-(styrene)-6/ocfc-poly(amide). The condensation was slow the probability of finding functional groups at an effective distance is small. 

Diamino derivatives of carbohydrates have been employed for polycondensation reactions with carboxyl-activated aliphatic and aromatic dicar-boxylic acids. The resulting polyamides are of the AABB type (nylons-m,n analogs), and therefore, the regio- and stereoregularity in the polyamide chain is determined by the configuration of the carbohydrate precursor. When such a molecule lacks a C2 axis of symmetry, random polymerization leads to nonstereoregular polyamides. 

Improvement of Membrane Selectivity (UTC-70R) Tb improve membrane selectivity, polyamide chains in the membrane are prefened to be packed tightly. We found that a certain posttreatment aimed to cleavage hydrogen bond of polyamide and reorder polymer chains effectively improved membrane selectivity of UTC-70 (Figure 8). This type of membrane are commercialized as "UTC-70R", and membrane performance is shown Figure 7. 

These data show that the dissociation energy of the urethane-type bonds is lower than that of -C-C- bonds from polyethylene or polypropylene. It is also two times lower than the dissociation energy of the bond from the polyamide chain. In this last case, the energetic barrier that must be overtaken in order as a elementary craek to appear is higher due to the supplementary orientation of the amorphous domains of fibres, realised by forced orientation during stretching. 

Because the rules for organic nomenclature determine the priority of naming different carbon chains from their relative lengths, the systematic names for type AABB polyamides depend on the relative length of the carbon chains between the amide nitrogens and the two carbonyl functions of the polymer for aUphatic nylon-Ayy, when x < the lUPAC name is poly[imino-R imino(l2y-dioxo-R )]. When x > then the name is... 

Most addition polymers are formed from polymerizations exhibiting chain-growth kinetics. This includes the typical polymerizations, via free radical or some ionic mode, of the vast majority of vinyl monomers such as vinyl chloride, ethylene, styrene, propylene, methyl methacrylate, and vinyl acetate. By comparison, most condensation polymers are formed from systems exhibiting stepwise kinetics. Industrially this includes the formation of polyesters and polyamides (nylons). Thus, there exists a large overlap between the terms stepwise kinetics and condensation polymers, and chainwise kinetics and addition (or vinyl) polymers. A comparison of the two types of systems is given in Table 4.1. 

Further variation is possible in the polymer structure and properties by using mixtures of the appropriate reactants such that the polymer chain can have different R and R groups. Thus polyamide structures of types XXXV and XXXVI are possible variations on structures XXXIII and XXXIV, respectively. A polymer such as XXXV or XXXVI has two different repeat units and is referred to as a copolymer the process by which it is synthesized is... 

Unusual properties of fully aromatic polyesters are observed if they have at least partially a rigid planar chain structure. In particular, they can form thermotropic liquid crystalline states (see Example 4-5). As already discussed in Sect. 1.2.4 an important structural prerequisit for LCPs of Type A in order to attain the liquid crystalline state of aromatic polyesters (and aromatic polyamides, see Example 4-14), is a rigid main chain according to the following construction principle ... 

Fully aromatic polyamides are synthesized by interfacial polycondensation of diamines and dicarboxylic acid dichlorides or by solution condensation at low temperature. For the synthesis of poly(p-benzamide)s the low-temperature polycondensation of 4-aminobenzoyl chloride hydrochloride is applicable in a mixture of N-methylpyrrolidone and calcium chloride as solvent. The rate of the reaction and molecular weight are influenced by many factors, like the purity of monomers and solvents, the mode of monomer addition, temperature, stirring velocity, and chain terminators. Also, the type and amount of the neutralization agents which react with the hydrochloric acid from the condensation reaction, play an important role. Suitable are, e.g., calcium hydroxide or calcium oxide. 

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