Polymer superstructure

The polymer superstructure influences its solubility. Askadskii and Matveev proposed a new criterion of solubility for linear polymers based on interaction of forces of a surface tension on wetting. The solubility parameter of polymer should be lower or equal to the work of rupture by solvent of a bond relative to a volume unit of the bond element. The condition of solubility can be expressed as follows ... 

This effect is explained by Inbrication action between elements of the polymer superstructure. The plasticizing effect was evident with abont 0.1% plasticizer in systems containing cellulose esters, and in mixtures of polypropylene and siloxane." " The most useful result of this effect is a decrease in viscosity,"" an increase in fatigue resistance," an improvement in impact strength," and in the adhesion of films." ... 

McCullough, R.D., and P.C. Ewbank. 1997. Self-assembly and chemical response of conducting polymer superstructures. Synth Met 84 (1-3) 311-312. 

Neely, W.D., Cousins, T.E., and Lesko, J.J. (2004), Evaluation of in-service performance of Tom s Creek bridge fiber-reinforced polymer superstructure , ASCEJ. Perf. Const. Facilities, 18(3), 147-158... 

Encapsulation of enzymes in various polymer superstructures (dendrimers, polymersomes, PICsomes, or LbL capsules) provides significant advantages, such as higher stability and preserved catalytic activity over longer periods of time than bulk conditions. The process of encapsulation/entrapment of biomolecules in various 3D supramolecular assemblies should not affect the stability of the final nanoreactor structure (which is driven by the chemical nature of the copolymer used for their formation). If necessary cross-linking procedures can be used to increase the stability. However, it is also necessary to determine if... 

Several polymer superstructure morphologies can be found in crystallizing a polymer lamellae, rods, sheet-like structures, hedrides or axialites, and spheru-lites. The formation of specific superstructures depends on molecular mass, crystallization condition, and structural regularity of the individual macromolecules. The polymer superstructures most likely to be met are lamellae, spherulites, and hedrites [1-3]. 

Figure 1. Self-assembled conducting polymer superstructures form from regioregular polythiophenes as confirmed by X-ray and light scattering studies.

Other workers indicated that anions can be exchanged after growth with minimal effect on conductivity, suggesting that the polymer superstructure is determined during synthesis, and the incorporation of other ions has minimal effect on this structure. 

Sheika, S. S. Imaging of Polymers Using Scanning Force Microscopy From Superstructures to Individual Molecules. VoL 151, pp. 61-174. 

SEM micrographs of two members of these polymers (HB and HBIB-50) are shown in Figure 7 to provide further evidence for superstructure on the micron level within the solution cast films. One can directly observe the surface of the spherulitic structure of the HB homopolymer as well as in that of the copolymer HBIB-50. Clearly, the level of structure (-5 pm) is well above that of the individual domains of either HB or HI and reflects the possible primary nucleation and subsequent growth behavior common to spherulitic semicrystalline polymers. The Hv patterns shown in... 

Formation of physical cross-links by the anchorage of chain ends in semicrystalline domains and production of permanent entanglements is shown in the HBIB block copolymers. No such arrangement exists for the inverted polymer HIBI. (No attempt has been made to show possible chain folding, or superstructure development of their... 

As an example of blends with attractive interactions, Fig. 65 shows a superstructure in which interactions between methacrylic acid groups and pyridine side groups of a polystyrene-fc-polybutadiene-fo-poly(f-butyl methacry-late-staf-methacrylic acid) (PS-b-PB-b-P(MAA-sfaf-fBMA)) triblock quater-polymer and a PS- -P2VP diblock copolymer lead to a wavy lamellar structure with cylinders from mixed P2VP and P(MAA-sfaf-fBMA) blocks [194],... 

The individual objects that compose the model are screws which simulate the molecules of the helical polymer their individual chirality is responsible for the spontaneous formation of the overall helical structure. In the model, the screws are left-handed and have a rather compact thread, that is, the pitch-to-diameter ratio of the individual screws is small In this case, left-handed screws generate a left-handed overall helical structure. If instead the thread is loose, left-handed screws may generate a right-handed superstructure (see discussion in Section 3). 

Another conductivity mechanism could be suggested for LB films of this polymer with Ag+ cations. Such cations can accept or release electrons easily, so in the layer of such cations the conductivity could be caused by electron transitions between the ions with different degrees of oxidation. With tunneling microscopy an anomaly in the dl/dV(V) curves near zero bias was discovered for the LB films in Ag form with an odd number of layers there was a conductivity peak some 150-200 mV wide (Figure 7.4, Curves 1, 3) but no anomaly for these same films with an even number of layers (Figure 7.4, Curve 2). For LB films with an odd number of layers the ordered superstructure of the scale 11.5 x 11.5 x lO cm has been found in a conductivity dl/dV (x,y) measurement regime. The scale of such a structure corresponds to 3 x 2 surface reconstruction (Figure 7.5). 

Figure 10. Illustration of influence of domain formation in block copolymers according to the models of Helfand and coworkers. The free energy is shown as a function of the size and separation of the domains of varying composition. (The spontaneous separations may be analogous to the way superstructure is formed in natural polymers of plants and animals.)...

Both synthetic and natural polymers have superstructures that influence or dictate the properties of the material. Many of these primary, secondary, tertiary, and quaternary structures are influenced in a similar manner. Thus, the primary structure is a driving force for the secondary structure. Allowed and preferred primary and secondary bondings influence structure. For most natural and synthetic polymers, hydrophobic and hydrophilic domains tend to cluster. Thus, most helical structures will have either a hydrophobic or hydrophilic inner core with the opposite outer core resulting from a balance between secondary and primary bonding factors and steric and bond angle constraints. Nature has used these differences in domain character to create the world around us. 

Considering the large field of polymer chemistry and the synthetic expertize available, the production of synthetic polymeric CSPs by generating either chiral polymeric superstructures and/or polymers containing chiral groups seems a promising field for further developments. 

For example, the aggregated structures of the solutions containing polymer-metal complexes and the colloidal dispersions of metal nanoparticles stabilized by polymers have been analyzed quantitatively (64). SAXS analyses of colloidal dispersions of Pi, Rh, and Pt/Rh (1/1) nanoparticles stabilized by PVP have indicated that spatial distributions of metal nanoparticles in colloidal dispersions are different from each other. The superstructure (greater than 10.0 nm in diameter), with average size highly dependent on the metal element employed, is proposed. These superstructures are composed of several fundamental clusters with a diameter of 2.0-4.0 nm, as shown in Figure 9.1.13 for PVP-stabilized Pt nanoparticles. 

Polymers are generally not discussed in this book. However, a polymer with rotaxane structures involving cyclodextrins in side chains 408 [36], pseudorotaxane superstructures [37], doubly twisted polyrotaxane [38] as well as infinite polyrotaxane network (Figure 8.2.5) [39] can be mentioned here. 

Polytetrafluoroethylene (PTFE) is an attractive model substance for understanding the relationships between structure and properties among crystalline polymers. The crystallinity of PTFE (based on X-ray data) can be controlled by solidification and heat treatments. The crystals are large and one is relieved of the complexity of a spherulitic superstructure because, with rare exceptions, spherulites are absent from PTFE. What is present are lamellar crystals (XL) and a noncrystalline phase (NXL) both of which have important effects on mechanical behavior. 

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