Polystyrene model studies

Hydrogenolysis of three different polystyrenes were studied (Table 3.4). The first two are standard polymers of low polydispersity and are considered as model... 

Secondary Reactions of Type 1 Photoinitiators Model Studies with Polystyrene... 

The amount of unreacted initiator that remains in a coating after photocuring is dependent on the initial concentration, the quantum yield, the irradiation time and the light source. To investigate how unreacted initiator affects the photostability of coatings, model studies with polystyrene were conducted (21). 

Hodge, I. M., and Huvard, G. S. (1983). Effects of annealing and prior history on enthalpy relaxation in glassy polymers. 3. Experimental and modeling studies of polystyrene. Macromolecules 16(3), 371-375. 

To prove the point, model studies were done to demonstrate that crosslinking via cationic initiation was indeed the reaction that competed with metathesis polycondensation. Substituted styrenes were used to test the hypothesis of cation formation, since styrene is a well-known catioiuc polymerizable alkene that gives an easily characterized product. When varions styrenes were treated with classic Lewis acidic catalyst systems like WCl6/EtAlCl2, only polystyrene was produced, whereas metathesis products (substituted stilbenes) were not observed (Scheme 4)." ... 

Thus crazing has been directly identified in typical rubber-modified plastics in a plane perpendicular to the direction of the applied stress and initiated at the rubber-matrix interface. These findings are quite consistent with macroscopic model studies performed by Matsuo et al. (1972), who studied the behavior of polystyrene-containing rubber balls (as an analog of ABS morphology). It was found that equatorial crazes developed in tension, as expected, and also that stress field interaction occurred when the balls were close together, resulting in a heavier craze density between the balls. This shows that a principal role of rubber particles is to induce many... 

The validity of scaling laws has been tested on several swollen network systems (Table 29.9). Munch et al. [99] studied the concentration dependence of the shear modulus for polystyrene model networks synthesized by copolymerization of styrene and divinylbenzene and swollen to equilibrium in benzene (good solvent for polystyrene). It was found that the modulus obeys a scaling law with equilibrium concentration, similar to that obtained for semidilute polymer solutions. The best fit to the equation G = Brpi yields... 

An important step in tire progress of colloid science was tire development of monodisperse polymer latex suspensions in tire 1950s. These are prepared by emulsion polymerization, which is nowadays also carried out industrially on a large scale for many different polymers. Perhaps tire best-studied colloidal model system is tliat of polystyrene (PS) latex [9]. This is prepared with a hydrophilic group (such as sulphate) at tire end of each molecule. In water tliis produces well defined spheres witli a number of end groups at tire surface, which (partly) ionize to... 

In numerous applications of polymeric materials multilayers of films are used. This practice is found in microelectronic, aeronautical, and biomedical applications to name a few. Developing good adhesion between these layers requires interdiffusion of the molecules at the interfaces between the layers over size scales comparable to the molecular diameter (tens of nm). In addition, these interfaces are buried within the specimen. Aside from this practical aspect, interdififlision over short distances holds the key for critically evaluating current theories of polymer difllision. Theories of polymer interdiffusion predict specific shapes for the concentration profile of segments across the interface as a function of time. Interdiffiision studies on bilayered specimen comprised of a layer of polystyrene (PS) on a layer of perdeuterated (PS) d-PS, can be used as a model system that will capture the fundamental physics of the problem. Initially, the bilayer will have a sharp interface, which upon annealing will broaden with time. 

This paper extends previous studies on the control of a polystyrene reactor by including (1) a dynamic lag on the manipulated flow rate to improve dynamic decoupling, and (2) pole placement via state variable feedback to improve overall response time. Included from the previous work are optimal allocation of resources and steady state decoupling. Simulations on the non-linear reactor model show that response times can be reduced by a factor of 6 and that for step changes in desired values the dynamic decoupling is very satisfactory. 

Any fundamental study of the rheology of concentrated suspensions necessitates the use of simple systems of well-defined geometry and where the surface characteristics of the particles are well established. For that purpose well-characterized polymer particles of narrow size distribution are used in aqueous or non-aqueous systems. For interpretation of the rheological results, the inter-particle pair-potential must be well-defined and theories must be available for its calculation. The simplest system to consider is that where the pair potential may be represented by a hard sphere model. This, for example, is the case for polystyrene latex dispersions in organic solvents such as benzyl alcohol or cresol, whereby electrostatic interactions are well screened (1). Concentrated dispersions in non-polar media in which the particles are stabilized by a "built-in" stabilizer layer, may also be used, since the pair-potential can be represented by a hard-sphere interaction, where the hard sphere radius is given by the particles radius plus the adsorbed layer thickness. Systems of this type have been recently studied by Croucher and coworkers. (10,11) and Strivens (12). 

In a study aimed at the identification of products of free radical reactions with polystyrene- and aromatic-based PEMs using model compounds, Hiibner and Roduner observed the addition of free radicals to the aromatic rings, preferentially in the ortho position to alkyl- and RO-substituents (in polystyrene- and aromatic-based PEMs, the para position is blocked by the presence of the sulfonic acid group). This study demonstrated the combined ortho-activation by these substituents and the meta-directing effect... 

---