Random E-P copolymer

Random E/P copolymers consist of PP chains in which small amounts of ethylene (C2) are more or less randomly distributed. The C2 units act as defects for the regularity of chain configuration and reduce the overall crystallinity of the polymer. 

Although it is reasonable to expect differences in degradation behaviour between random and heterophase copolymers, literature seldom defines clearly the nature of copolymers studied. Well characterized heterophase E-P copolymers, however, are of very recent origin. 

Commingled post-consumer recyclates containing mixtures of polymers that differ in structure and polarity with limited miscibility have low tensile and impact properties. Both nonreactive and reactive compatibilizers are applied. Nonreactive compatibilizers are diblock or multiblock copolymers. Compatibilizers principally consisting of mixtures of POs are of major interest for recyclates. Random E/P eopolymers are effective compatibilizers for LDPE/PP, HDPE/PP or LLDPE/PP blends [94], Other examples are given in Table 12. 

As an example, consider a uniform parent distribution p(°) (a) = const, which can be written as p (o) = p /2, using the fact that pj, = do p (a). Then pf 1 — pff / 3 and p =p /5 and so a tricritical point occurs if the overall density (i.e., the copolymer volume fraction) is pf = 3/(2r + 3). Figure 13 shows the coexistence curve calculated for this parent (with r = 1), which clearly shows the tricritical point at the predicted value X1 = l/(2/4° ) = r + 3/2 = 2.5. Our numerical implementation manages to locate the tricritical point and follow the three coexisting phases without problems we take that as a signature of its robustness [58]. Note that the tricritical point that we found is closely analogous to that studied by Leibler [57] for a symmetric blend of two homopolymers and a symmetric random copolymer that is, nonetheless, chemically monodisperse (in the sense that o = 0 for all copolymers present). In fact, in our notation, the scenario of Ref. 57 simply corresponds to a parent density of the form p (o) S(o — 1) + S(o +1), with the copolymer (o = 0) now playing the role of the neutral solvent. 

It turned out that many statistical properties of protein-like and random copolymers with the same HP composition are very different. In order to be able to distinguish whether this difference is due to the special sequence design described above, or just due to the different degree of blockiness, one can introduce for comparison also the random-block primary sequence. The random-block HP copolymers have the same chemical composition and the same average length L of uninterrupted H or P sequence as protein-like copolymers, but in other respects the HP sequence is random. In [18], the distribution of block length X was taken in the Poisson form /(A) = e LLl/ l. 

Heat-resistant [218] soft foams were prepared from the blends of hdPE with E-P random copolymers. The azodicarbanamide acts as a thermal antioxidant and the crosslinking of the blend was increased by electron beam radiations and foamed at 225 °C with 2320% expansion. A blend of 35 wt.% PE-PP (8 92), 15 wt.% E-P block copolymers, and 50 wt.% EPDM showed accelerated weathering resitance [219] 1000 h probably due to crosslinking between constituents of the block copolymer, polyblend and EPDM. The effect of filler and thermodynamic compatibility on kaolin-filled PE-PP blend was studied by Lipatov and coworkers [220]. The thermodynamic interaction parameter (%) decreased and thermodynamic stability increased by filler addition, the degree of crystallinity decreased with increasing thermodynamic compatibility of the components due to sharp decrease in the phase separation rate during cooling. 

Bly,R.M., Kiener,P.E., Fries,B.A. Near-infrared method for analysis of block and random ethylene-propylene copolymers. Anal. Chem. 38,217-220 (1966). 

The lattice parameters vary continuously with composition of the blend and the cocrystaUization process is ascribed to the closeness of the crystaUization rate of both species The tendency to cocrystaUize increases with increasing HDPE concentration ° P(E)q43(K)q5. is a random copolymer composed of phenyl ether and phenyl ketone units p Copolymer of styrene and p-methyl styrene containing 30 mol% of the latter comonomer... 

The hydrogenation of cis-1,4 copolymers of B and I would lead to polyolefins with composition and sequence distribution consisting of ethylene (E) blocks and alternating ethylene/propylene (E/P) blocks. These novel polyolefins are difficult or almost impossible to obtain directly by simple polymerization of E and P monomers using any existing polymerization catalysts. Since structural variations in these polyolefins, such as composition aind monomer sequence distribution, would significantly affect the polyolefin properties, the hydrogenated cis-1,4 B/I copolymers with uniformly random distribution of E and E/P imits may serve as model polymers to study structure-property relationships and be useful as polymers with unique properties. 

The properties of H(B/I) random copolymers can be varied from those of semi-crystalline plastics (i.e., linear LDPE with methyl branches) to those of essentially amorphous elastomers. A gradual transition from translucent thermoplastics to transparent rubbers wais observed as the molar ratio of E (or HB) to E/P (or HI) decreased. 

Bly, R.M., P.E. Kiener, and B.A. Fries, Near Infrared Method for Analysis of Block and Random Ethylene-Propylene Copolymers. Ana/. Chem., 1966. 38 217-220. 

Pollino, J.M., Stubbs, E.P, and Week, M. (2004) One-step multifunctionaUzation of random copolymers via self-assembly. Journal of the American Chemical Society, 126,563—567. 

These copolymers, random and completely amorphous, with respect to their membrane gas permeabilities are the intermediates between the corresponding homopolymers, i.e. p-DMePO and p-DPhPO. The permeability coefficients of the copolymers are listed in Table 3. 

Copolymers of VF2 with trifluoroethylene are randomly added copolymers. Those containing a mole fraction of VF2 of 50-80% have been widely studied. Since they contain a greater proportion of the comparatively bulky fluorine atoms than PVF2 their molecular chains cannot accommodate the tg+tg conformation and crystallize at room temperature in the ferroelectric phase with the extended all-trans planar conformation [37] with small statistical deviations away from that plane, i.e. copolymers of VF2 with F3E crystallize essentially with the same conformation as P-PVF2. 

As mentioned above for copolymer based blends the quantities e and r in definitions (9) have to be replaced by number-averaged quantities . For a blend of a homopolymer A and a random copolymer B, P(CpD, p), comprising segments of type C and D with mole fractions p and (1 — p), respectively, the generalization of the parameters can be done along the same lines as sketched in Appendix III. It is useful to introduce the following notations ... 

The equations which describe the lossy modulus behavior product and maximum temperature bandwidth for random copolymers of P(EMA-co-EA) and a maximum E"maX of PnBA. The product of T. /2N and E"max(dy/cm2 x 10" ), simi-... 

Conformations of the polymers were studied by CD and optical rotation measurements. Poly-L-lysine is known to exist in disordered, helical and P-conformation, depending on the temperature, pH of the system and the solvent used. The side chain of the polymer has a significant effect on the backbone conformation. At neutral pH, poly-L-lysine exists in a random coil structure while at pH above 10, the e-amino group becomes a neutral form and the polymer undergoes transition to a helical structure. In order to elucidate the effect of base substituents on the conformation of poly-L-lysine, CD spectra of the copolymer were measured. 

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