Ideal crosslinked‐polymers and their characterization in free‐radical monovinyl‐divinyl copolymerizations

Abstract

The critical conditions in which the classical Flor y-Stockmayer gelation theory (F-S theory) is applicable to monovinyl-divinyl copolymerizations were pursued in detail. The resulting prepolymers or precursors of ideal crosslinked-polymers were characterized as standard polymers for the discussion of network formation in free-r adical monovinyl-divinyl copolymerizations. Methyl methacrylate was copolymerized with a small amount of ethylene dimethacrylate, butylene dimethacrylate or nonapropyleneglycol dimethacrylate in the presence of lauryl mercaptan, a chain transfer agent to reduce the occurrence of a thermodynamic excluded volume effect and intramolecular crosslinking as the primary and secondary factors, respectively, for the greatly delayed gelation in the free-radical monovinyl-divinyl copolymerizations and, moreover, to keep the primary chain length constant by inhibiting a gel effect. The ratio of the actual gel point to the theoretical one reached 1.1, supporting the validity of F-S theory. The resulting prepolymers were subjected to SEC-MALLS analysis to determine the molecular weights, the molecular-weight distributions and the radii of gyration; the correlations of molecular weight vs. elution volume and radius of gyration vs. molecular weight were useful for the characterization of the precursors of ideal network-pol y mers.

Graft polymerization of allyl benzoate using poly(allyl benzoate-co-2,2′-azobis[N-(2-propenyl)-2-methylpropionamide]) as polymeric azo-initiator

“…However, as a technique it is not always applicable to our graft polymerization systems because the structure of resulting polymer changes from a linear to a branched form with the progress of polymerization. On the other hand, SEC-MALLS is expected to be a very useful and efficient tool in characterizing our graft copolymers, because the use of MALLS, as an absolute detector, enables the molecular weight and MWD to be determined directly without any calibration 5) . Fig.…”

Degradation of Ultrahigh Molecular Weight Poly(styrene-co-m-divinylbenzene)s as Network-Polymer Precursors in SEC Columns

“…1 The actual gel point should be close to the theoretical one if the experiment were done under the polymerization conditions in which the polymer concentration, at the theoretical gel point, would be high enough to reduce the significance of a thermodynamic excluded volume effect as a primary factor and, furthermore, the intramolecular crosslinking preceded by the intermolecular crosslinking could be suppressed. Our interpretations are verified for monomethacrylate/dimethacrylate, 4,5 monoacrylate/diacrylate, 6 and St/m-DVB 2 copolymerizations, in which the results obtained are discussed in terms of ideal network formation according to FS theory.…”

“…On the other hand, SEC equipped with a multiangle laser light scattering (MALLS) device (SEC-MALLS) is expected to be a very useful and efficient tool in characterizing our prepolymers because the use of MALLS, as an absolute detector, enables the molecular weight and MWD to be determined directly without any calibration. 5 During the progress of our investigation, we noticed that the degradation of poly(St-co-m-DVB) prepolymer of ultrahigh molecular weight obtained at the conversion close to the gel point occurred significantly in SEC columns. That is, the molecular weights determined by both SEC-MALLS and light scattering (LS) measurements were compared in detail.…”

Further Discussion of the Specific Polymerization Behavior of Triallyl Isocyanurate. Enhanced Occurrence of Intermolecular Crosslinking at an Early Stage of Polymerization

“…Thus, in the bulk polymerizations of multiallyl compounds the gelled polymers are usually obtained above 20% conversion, e.g., the gel points are estimated to be 23.5, 22.0, and 21.3%, respectively, for DAT, 15 triallyl trimellitate, 16 and TAC 4 polymerizations. Furthermore, the experimental results are quite high in com- parison with the theoretical gel points calculated from Gordon's equation as exemplified by DAT polymerization.…”

“…On the other hand, SEC-MALLS is expected to be a very useful and efficient tool in characterizing our prepolymers because the use of MALLS, as an absolute detector, enables the molecular weight and MWD to be determined directly without any calibration. 11 Thus, this article deals with the further discussion of the specific polymerization behavior of TAIC; the occurrence of intermolecular crosslinking reaction was explored in detail as compared with the polymerization behavior of diallyl terephthalate (DAT) as a typical multiallyl compound. In the polymerization of TAIC, the conversion dependence of the MWD profiles of resulting prepolymers was different from that in DAT polymerization, i.e., the MWD curves were broadened toward a higher molecular weight side at an earlier stage of polymerization as a reflection of the occurrence of intermolecular crosslinking reaction.…”