Effect of Comonomer

The expression Flory used to describe the effect of comonomer on polymer melting is based on a more general expression for polymer diluent systems which has become known as the Flory-Huggins expression, namely 

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Fig. 3. Effect of comonomer stmcture on the glass-transition temperature of VDC copolymers (72), where A represents acrylonitrile B, methyl acrylate ...

Figure 5 Effect of comonomer concentration on copolymerization of acrylamide with EAEA-HCl. O Rp, % = [tj].

Figure 9. Effect of comonomer feed ratio on the rate of polymerization in hexane at 30°C.

It is interesting to analyse the effect of comonomer nature on the plastic behaviour of the copolymers. 

Recently, Siu et al. [139] studied the effect of comonomer composition on the formation of the mesoglobular phase of amphiphilic copolymer chains in dilute solutions. The copolymer used was made of monomers, N,N-diethylacrylamide (DEA) and N,N-dimethylacrylamide (DMA). like PNI-PAM, PDEA is also a thermally sensitive polymer with a similar LCST, but PDMA remains water-soluble in the temperature range (< 60 °C) studied. At room temperature, copolymers made of DMA and DEA are hydrophilic, but become amphiphilic at temperatures higher than 32 °C. Before the association study, each P(DEA-co-DMA) copolymer was characterized by laser light scattering to determine its weight average molar mass (Mw) and its chain size ( Rg) and (R )). The copolymer solutions (6.0 x 10 A g/mL) were clarified with a 0.45 xm Millipore Millex-LCR filter to remove dust before the LLS measurement. 

After investigating the effect of comonomer composition on the chain association as well as the effect of comonomer distribution on the chain folding, Siu et al. [141] extended their study to the effect of comonomer distribution on the chain association. They copolymerized NIPAM and vinyl pyrroli-done (VP) at temperatures, respectively, higher and lower than the LCST, which resulted in segmented and random VP distributions on the PNIPAM chain backbone. The synthesis characterization of these PNIPAM-co-VP amphiphilic copolymers with a similar chain length and comonomer composition, but different comonomer distributions, were described in previous sections. 

The immobilization of MTO on poly(vinylpyridine) or its oxide was also tested, but here, the conversions are a bit lower [56]. Furthermore, the effect of comonomers in PVP, such as butylmethacrylate or ethyleneglycoldimethacrylate, was explored. With some of these systems, excellent selectivity for the epoxide was... 

Table II. Effect of Comonomer Composition on Conversion to Block Polymers...

Fig. 5 Effect of comonomer content on the coalescence behavior of polyethylene copolymers at ramped temperature (111-226.5°C at ll°C/min). The relative methyl content for PE9-0, PEIO-O, and PEI 1-0 is 0.95, 0.56, and 0.15, respectively. (Erom RQfP )...

PEC, PPO, and PS are amorphous materials as normally melt processed, a fact which prevents the use of melting point depression analyses for experimentally determining AHnix or B for the blends with PS. Isotactic polystyrene, i-PS, is able to crystallize, is miscible with PPO, and has been successfully used to determine the parameters related to AHaix (7,12.18). This study shows that i-PS is also miscible with PEC copolymers which contain up to 20 moleX trimethyl comonomer. This fact permits the use of i-PS melting point depression analysis to determine the effect of comonomer content on AHaix with i-PS. 

The development of the concepts of run number, average sequence lengths and triad distributions would be of little more than academic interest if they could not be usefully applied. The concept of run number is most valuable in a consideration of the effect of comonomer content versus branch length in affecting polyethylene density. The following section utilizes the run number in a correlation with a number of polyethylene physical properties. 

Incorporation of comonomer units into the polyoxymethylene chain leads to a considerable decrease of the melting temperature 139). The effect of comonomer structure and concentration on the melting temperature is shown in Table 7.18. 

The assumption that one of the monomer units is excluded from the polymer crystal can entail several consequences. In this case, the, the size of the crystal is limited by the sequence length of the crystallizing monomer units, so the effect of comonomer concentration becomes mixed up with the effect of crystal size. In addition, if one of the units is excluded, it will probably reside at the crystal surface and affect the melting point. In many cases, comonomer units get included in the crystal, for example polypropylene in polyethylene. Thus, the situation is more complicated than what is described by the mathematics in this section. 

One of the features of olefin copolymerization kinetics is the effect of comonomer on the rate of ethene or propene polymerization during ethene/a-olefin or propene/ a-olefin copolymerization, i.e., the so-called comonomer effect (CEF). The rate enhancement of ethene or propene polymerization in the presence of a comonomer is observed for conventional ZN catalysts [80, 113-123] and for homogeneous [124-133] and supported metallocenes [134—136] and post-metallocenes catalysts [137-140]. The increase in activity was remarked in the presence of such comonomers as propene, 2-methylpropene, 1-butene, 3-methylbutene,4-methylpentene-l, 1-hexene, l-octene,l-decene, cyclopentene, styrene, and dienes. 

Feil, H. et al, 1993. Effect of comonomer hydrophilicity and ionization on the lower critical solution temperature of A-isopropylacrylamide copolymers. Macromolecules, 26(10), 2496-2500. 

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