Intramolecular cyclization of styrene–p‐divinylbenzene copolymers

Abstract

Styrene has been copolymerized at low conversion with minor quantities of p‐divinyl‐benzene (p‐DVB) in (10–15%) solution in toluene and cyclohexane. Under these conditions the molecular weight of the polystyrene formed in the absence of p‐DVB was controlled by chain transfer, and the copolymerization coefficients of the styrene and the p‐DVB agreed with previous work. Polymer molecular weights were studied as a function of conversion. At very low conversions the number‐average (2.2 × 105) and the weight‐average (4.4 × 105) molecular weights were unaffected by substituting some of the styrene by p‐DVB, but as the reaction continued M̄n increased slowly and M̄w much faster. On the other hand, even at the lowest conversions the intrinsic viscosity was drastically reduced by the introduction of p‐DVB, and the radius of gyration, as measured by light scattering, fell. Infrared studies on the polymer show that the concentration of pendent double bonds in low‐conversion copolymers is about half of the doubly substituted phenyl groups. It is concluded that the first polymer chains formed are extensively cyclized with the formation of a relatively large number of small rings.

Effect of Intramolecular Crosslinks on Microgel and Macrogel Formation by Photocrosslinking Reaction in Solution

“…For CEMA= 12mol% copolymer as shown in Table II 68 mer which form microgels as the crosslinking proceeds, the dimension of polymer coils decreases despite the large value of M w· This behavior is attributed to the increase of the contraction caused by intramolecular crosslinking overcoming the increase of expansion caused by intermolecular crosslinking. To evaluate the net contraction of polymer chains due to intramolecular crosslinking, the contraction ratio, g, is given by eq 2 as reported previously, 15 (2) The values of (s 2 )c, are those of (s 2 ) for irradiated polymers given in Figure 9. The values of (s 2 ) 1 were calculated with the value Figure 10.…”

“…In the radical copolymerization of styrene and divinylbenzene in solution, the extent of competition between intra-and intermolecular crosslinking and intramolecular cyclization between adjacent units has been discussed. 2 · 3 • 5 White et al 2 have reportd that the probability of intramolecular cyclization is rather high, whereby the number of elastically effective network chains is reduced. Horie et al 3 have also revealed three kinds of modes for crosslinking from an experimental study on the crosslinked copolymerization of methylmethacrylate (MMA) with ethylene dimethacrylate (EDMA) in bulk and in toluene.…”

Innermolekular vernetzte Makromoleküle (Mikrogel): Synthese, Eigenschaften und Nachweis in Gemischen

“…1st der Wert zw,l der unverzweigten, genugend hochmolekularen Molekule bei der bestimmten Konzentration c bekannt, so erkennt man den Volumenbruch qz des Gels im Polymerengemisch aus dem dann gemessenen z , nach der Beziehung Aus den Gleichungen (13), (14) und (15) …”

Chemistry of Siloxane Amide as a New Curing Agent for Epoxy Resins: Material Characterization and Properties

“…In continuation of our earlier studies21,22 aimed at the solventless curing of the epoxy resins, this also gives a clear homogenous mixture when blended together at room temperature without using any solvent. The disadvantage of carrying out the crosslinking reaction in solution is that imperfections like intramolecular loop formation of the chains and void formations can occur, which will greatly reduce the tensile strength and ultimate elongation 23,24. We have investigated the use of SA amine as a curing agent for DGEBA along with DDS.…”