Pseudo-copolymer

Note Where appropriate, adjectives specifying the types of copolymer may be applied to pseudo-copolymer. The term statistical pseudo-cqpo/ywer, for instance, may be used to describe an irregular polymer in the molecules of which the sequential distribution of configurational units obeys known statistical laws. 

Finally, it should be mentioned that there exist two other routes for the synthesis of copolymers. First the partial chemical conversion of homopolymers (see Sect. 5.1), for example, the partial hydrolysis of poly(vinyl acetate). Secondly, by homopolymerization of correspondingly built monomers. An example for these macromolecular compounds, sometimes called pseudo-copolymers, is the alternating copolymer of formaldehyde and ethylene oxide synthesized by ringopening polymerization of 1,3-dioxolane. 

The fact that the function I(q) has a maximum has been verified by neutron scattering on a sample, consisting of pseudo copolymers obtained by linking two polystyrene chains, one deuterated and the other non-deuterated. This result shows clearly how compensations between intramolecular and inter-molecular contributions come into play. 

A copolymer is derived from more than one species of monomer. The term copolymer is strictly connected with the synthesis of the polymer. It does not refer to the composition of the polymers, e.g. distribution of configurational units (pseudo-copolymer). 

The second type of solution polymerization concept uses mixtures of supercritical ethylene and molten PE as the medium for ethylene polymerization. Some reactors previously used for free-radical ethylene polymerization in supercritical ethylene at high pressure (see Olefin POLYMERS,LOW DENSITY polyethylene) were converted for the catalytic synthesis of LLDPE. Both stirred and tubular autoclaves operating at 30—200 MPa (4,500—30,000 psig) and 170—350°C can also be used for this purpose. Residence times in these reactors are short, from 1 to 5 minutes. Three types of catalysts are used in these processes. The first type includes pseudo-homogeneous Ziegler catalysts. In this case, all catalyst components are introduced into a reactor as hquids or solutions but form soHd catalysts when combined in the reactor. Examples of such catalysts include titanium tetrachloride as well as its mixtures with vanadium oxytrichloride and a trialkyl aluminum compound (53,54). The second type of catalysts are soHd Ziegler catalysts (55). Both of these catalysts produce compositionaHy nonuniform LLDPE resins. Exxon Chemical Company uses a third type of catalysts, metallocene catalysts, in a similar solution process to produce uniformly branched ethylene copolymers with 1-butene and 1-hexene called Exact resins (56). 

The products have been described as pseudo-random copolymers. The reason for this is that successive head-to-tail styrene-styrene insertions do not occur. The structure may thus be formally represented as... 

Unusual reactivities of mechano-radicals have been reported in a few instances. To explain the pseudo first-order kinetics and the high yield of linear block copolymers formed during the mechanochemical degradation of a mixture of... 

Pseudo Kinetic Rate Constant Method for Copolymers with Long Branches... 

Plots of the concentration of carboxylate formed vs. time were drawn for each copolymer, and the initial rates of hydrolysis were determined by measurement of the slope of the tangent to the curve at zero time. The pseudo-unimolecular rate constant (K) is given by ... 

Binder WH, Bemstorff S, Kluger C, Petraru L, Kunz MJ. Tunable materials from hydrogen-bonded pseudo block copolymers. Adv Mater 2005 17 2824-2828. 

The rate of dispersion (co)polymerization of PEO macromonomers passes through a maximum at a certain conversion. No constant rate interval was observed and it was attributed to the decreasing monomer concentration. At the beginning of polymerization, the abrupt increase in the rate was attributed to a certain compartmentalization of reaction loci, the diffusion controlled termination, gel effect, and pseudo-bulk kinetics. A dispersion copolymerization of PEO macromonomers in polar media is used to prepare monodisperse polymer particles in micron and submicron range as a result of the very short nucleation period, the high nucleation activity of macromonomer or its graft copolymer formed, and the location of surface active group of stabilizer at the particle surface (chemically bound at the particle surface). Under such conditions a small amount of stabilizer promotes the formation of stable and monodisperse polymer particles. 

The dendrimer droplets were used as a tool to examine surface heterogeneity on the nanoscale [319]. Figure 32 shows two pairs of SFM images of the droplets deposited on mica (a,b) and a copolymer film (c,d), respectively. On mica, the hydroxyl terminated dendrimer showed the autophobic or pseudo-partial wetting behaviour as the droplets sit on a thin film of the same material [312,320]. 

Fig. 18 Schematic two-dimensional presentation for crystallization of the interphase. With crystallization of the interphase in the open-orthorhombic phase, contraction in the orthorhombic crystalline lattice occurs. This results in the formation of dense orthorhombic or monodinic phase (see Figs. 15 and 16). In branched alkanes, because of the relatively sharp folds, the amount of chains contributing to the interphase is considerably less, which corresponds to the low intensity of the reflection assigned to the pseudo-hexagonal phase (see Figs. 12 and 14), while the phenomenon of concentration of the lattice with crystallization of the interphase is the same as in copolymers...

It is to be noted that the reflection assigned to the new phase in butyl branched alkanes is relatively weak compared to the reflections observed for the new phase in ethylene-1-octene copolymer (5.2 mol %). As explained in this chapter, we attribute the new phase to the crystallization of transient layer (butyl branches and fold surface). Considering the anticipated tight folds for butyl branched alkanes, the amount of crystallizable entities in the branched alkanes would be much less than in the ethylene-1-octene copolymers where the loose folds are expected. We would like to mention that, considering the d-value and intensity of the pseudo-hexagonal phase in branched alkanes, this reflection may be referred to as open-orthorhombic phase. 

---