A polymer (from Greek poly, many, meros, part, segment) is a substance whose molecules are at least approximately multiples of low molecular weight units. The unity of low molecular weight monomer. If the polymer is strictly uniform molecular weight and molecular structure, degree of polymerization is indicated by a Greek numeral, according to the number of monomer units it contains, so talk of dimers, trimers, tetramer, pentamer and beyond. The term polymer refers to a combination of an unspecified number of drives. Thus, the trióximetileno, is the trimer of formaldehyde, for example.
If the number of units is very large, it also uses the expression large polymer. A polymer does not need to consist of individual molecules all of the same molecular weight, and need not all have the same chemical composition and the same molecular structure. There are natural polymers such as certain globular proteins policarbohidratos, whose individual molecules all have the same molecular weight and the same molecular structure, but the vast majority of important natural and synthetic polymers are mixtures of polymer components counterparts. The small variability in chemical composition and molecular structure is the result of the presence of end groups, branches occasional variations in the orientation of monomeric units and the irregularity in the order in which a succession of different types of such units copolymers. These varieties are generally not affect the final product properties , however, has discovered that in some cases there were variations in copolymers and certain crystalline polymers.
isomers polymers are polymers that have essentially the same percentage composition, but differ in the placement of atoms or groups of atoms in molecules. The vinyl polymers such isomers can be distinguished in the guidelines (head to tail, head to head, tail to tail, or random mixtures to of two) of consecutive segments (monomer units):
0 comments:
Post a Comment