In thermoplastics, the polymer chains are held together by secondary bonds which form physical crosslinks such as hydrogen bonds, which are reversible. The physical crosslinks dissipate when heated past a critical temperature but reform when cooled, granting thermoplastics their reprocessable nature. ...
The folded chains are held together by localized chemical bonds. The crystalline regions are connected by amorphous regions. This definition of crystalline is different than that used for metals and ceramics. Examples of crystalline polymers include high-density polyethylene (HDPE), polypropylene (PP),...
chemical structure of polyvinyl chloride (PVC)Industrial polymers are synthesized from simple compounds joined together to form long chains. For example, polyvinyl chloride is an industrial homopolymer synthesized from repeating units of vinyl chloride. ...
Polymers are all created by the process of polymerization wherein their constituent elements called monomers, are reacted together to form polymer chains i.e., 3-dimensional networks forming the polymer bonds. Materials of Engineering refers to selecting the correct materials for the application in ...
(MW) greater than about 5000 g/mol or an average of more than 100 repeat units per molecule; and unlike low MW compounds, polymers consist of a distribution of chainlike molecules of differing MW’s. Generally the repeat units are held together by covalent chemical bonds in the form of ...
polymer chains, as evidenced by the positive and negative Cotton bands in the CD spectra (Figs.2and7), may serve to further enhance the chiroptical response, which leads to a greater contribution from the magnetic transition dipoles and electronic quadrupole transition to the CP dissymmetry. ...
5b, very narrow DOS distributions, such as those resulting from single polymer chains48, lead to narrower R ct curves with a reduced resistance to charge transfer (increased rate constant). Increasing σ broadens the R ct curve, shifts the minimum toward more negative energies (higher positive ...
Polymer systemscan be developed into a variety of functional forms to meet industrial and scientific applications. In general, they are presented in four common physical forms: (1) linear free chains in solution, (2) covalently or physically cross-linked reversible gels, (3) micro andnanoparticles...
Plasma treatment can introduce functional groups, such as silanes or carbon nanotubes, to the surface of polymers, which can enhance their mechanical strength by increasing the intermolecular interactions between the polymer chains and reinforcing their structure [154]. 10.6. Plasma-Modified Natural ...
“backbone” of the chain. In most cases polymers are made up ofcarbonbackbones—that is, chains of carbon (C) atoms linked together by single (C―C) or double (C=C) bonds. In theory, carbon chains are highly flexible, because rotation around carbon-carbon single bonds allows the ...