Low-molecular-weight polymers

In a solid polymer, low-molecular-weight species diffuse with D 10 7— 10 9cm2 s 1 [67]. Segments of a macromolecule with the free valence diffuse still more slowly (T>eff 10 9 10 12cm2 s-1)- With the lifetime of P02 of 10-100 s, the distance covered by this radical... 

PIB (structure 5.57) was initially synthesized in the 1920s. It is one of the few examples of the use of cationic catalysis to produce commercial-scale polymers. Low-molecular weight (about 5000 Da) PIB can be produced at room temperature, but large chains (over 1,000,000 Da) are made at low temperatures where transfer reactions are suppressed. 

Polymer/Low Molecular Weight Solute (Monomer)/Solvent (System A). 143... 

Nonpolar, noncrystalline synthetic polymers, hydrocarbon polymers, low molecular weight polymers Toluene (benzene3 or chloroform3 LiChrospher Si Merck... 

Equation (6.134) indicates that the physicochemical properties of drug, solvent, and polymer influence the overall release kinetics. The main key property governing swelling and erosion is the molecular weight of the polymer. Low-molecular-weight water-soluble polymers may provide synchronized swelling and erosion processes (e.g., polyethylene oxide < 2 x 106). However, those properties cannot be easily... 

B. Polymer-low molecular weight component-water Polypropylene glycol Potassium phosphate... 

Polyisobutylene is a synthetic polymer. Low-molecular-weight grades are soft and gummy high-molecular-weight... 

A final advantage of the vapor concentrator is that it can enhance the selectivity of the sensor. Clearly, the method is only effective for compounds that can be trapped on a sorbent polymer. Low molecular weight vapors such as methane, ethane, and propane are not readily trapped and thus will not be enriched. Likewise, very high molecular weight vapors will not be easily desorbed from the trap and thus will actually be diminished in concentration. 

T. Kajiyama, H. Kikuchi, and K. Nakamura, Photoresponsive electrooptical effect of liquid crystalline polymer/low molecular weight liquid crystal composite system, Proc. SPIE 1911, 111-121 (1993). 

The ideas of regular mixtures find application in the description of the properties of the system polymer+low-molecular-weight liquid (P+LMWL). 

Phase equilibrium in the crosslinked polymer + low-molecular-weight liquid system... 

State diagram polymer+low molecular weight liquid... 

While the lamellar structures in the spherulites are the analogue of the single crystals, the folding of the chains is much more irregular, as will be developed further in Section 6.6.2.3. In between the lamellar structures lies amorphous material. This portion is rich in components such as atactic polymers, low-molecular-weight material, or impurities of various kinds. 

A limitation of polyisobutene is its tendency to cold flow and, as a result, the polymer finds little use in self-supporting form. Applications are restricted mainly to adhesives, fabric and paper coatings, and blends with other polymers. Low molecular weight polyisobutene is also used in lubricants and as a tackifier. 

In addition to the high molecular weight polymers, low molecular weight liquid polymers have been available since about 1949 and these have important applications in sealants, caulking compounds, rocket propellants, and as flexibilizers for epoxide resins as well as castable rubbers. These liquid rubbers are obtained by controlled chain scission of high molecular weight materials. 

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