Ribbon polymers

The unique structure of ribbon polymers poses a challenge to classical methods of polymer synthesis and characterization. Additionally, there exists an urgent need for polymers with unconventional structure in order to achieve macromolecular materials with tailor-made chemical and physical properties. 

In the crystal, trimethyltin methoxide is a linear polymer, and dimethyltin dimethoxide is a dimer. The cyclic dialkyl-l,3,2-dioxastannolanes, which are formed from 1,2-diols, are important in regiospecific synthesis, particularly in carbohydrate chemistry. Their degree of association is determined by steric factors in the solid state, l,l-di-n-butyl-l,3,2-dioxastannolane is a 6-coordinate ribbon polymer, but the di-tert-butyl analog is a 5-coordinate dimer (19). Methyl 4,6-0-benzylidene-2,3-C-dibutylstannylene-Q -D-glucopyranoside is a 5-cordinate dimer, but methyl 4,6-0-benzylidene-2,3-0-dibutylstannylene-Q -D-mannopyranoside is a pentamer containing three, medial, 6-coordinate and two, terminal, 5-coordinate tin atoms. 

The complex [Cu(SCN)(dpt)]. [dpt = 2,4-bis(4-pyT-idyl)-1.3.5-triazine] exhibits structural supramolecular isomerism, with the two isomers adopting either a three-dimensional lattice A or a one-dimensional ribbon polymer Isomer A exhibits N3S binding via two dpt... 

The ribbon polymer is related to the less-flexible ladder and sheet polymers discussed before. One might expect very much different viscous behavior of such molecules in the melt. The interpenetrating networks [8] can have interesting elastic properties since each network may respond differently and interact with the other. The two-dimensional flexible polymers have recently been explored. They also belong to the sheet-like polymers. 

There have been many attempts to use pyrolysis in a controlled manner to produce molecularly well-defined materials an example is shown in Figure 4.8. Pyrolysis of the dianhydride monomer shown in Figure 4.8 under conditions of high temperature and high vacuum leads to the deposition of thin, lustrous, and chemically inert films which display an undoped conductivity of 250 (Qcm)" The expected structure was the ribbon polymer, poly(peri-napthalene), shown in Figure 4.8, but since hydrogen as well as carbon monoxide and carbon dioxide were eliminated this cannot be the real structure (12). 

Schultz J M and Kinloch D R (1969) Transverse screw dislocations A source of twist in crystalline polymer ribbons. Polymer 10 271-278. 

As the polymer molecular weight increases, so does the melt viscosity, and the power to the stirrer drive is monitored so that an end point can be determined for each batch. When the desired melt viscosity is reached, the molten polymer is discharged through a bottom valve, often under positive pressure of the blanketing gas, and extmded as a ribbon or as thick strands which are water-quenched and chopped continuously by a set of mechanical knives. Large amounts of PET are also made by continuous polymerization processes. PBT is made both by batch and continuous polymerization processes (79—81). 

Light-Duty Recreational Surfaces. Artificial surfaces intended for incidental recreational use, eg, swimming pool decks, patios, and landscaping, are designed primarily to provide a practical, durable, and attractive surface. Minimum cost is a prime consideration and has driven the quaUty of some such products to a low level. Most surfaces in this category utilize polypropylene ribbon and a tufted fabric constmction (see Olefin polymers, polypropylene). ... 

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