Free-Radical Cross-Linking Polymerization of Diallyl Terephthalate in the Presence of Microgel-like Poly(allyl methacrylate) Microspheres

Abstract

The cross-linking polymerization of diallyl terephthalate (DAT) was explored in detail in the presence of microgel-like poly(allyl methacrylate) (PAMA microsphere) as an extension of our continuing studies concerned with the elucidation of cross-linking reaction mechanism and the control of network formation in the free-radical cross-linking polymerization of multivinyl compounds. Thus, PAMA microspheres were prepared by the emulsion polymerization of AMA as reactive cross-linked polymer microspheres having abundant pendant allyl groups. The polymerization of DAT in the presence of microsphere was conducted in bulk using BPO as initiator at 80 °C. The gel-point conversion became higher with an increase in the feed amount of microsphere. No gel effect was observed. Variation of RI-monitored SEC curves with conversion suggested the copolymerization of the pendant allyl groups present on the surface of microsphere with DAT; this was also supported by light scattering and 1H NMR spectroscopy. The swelling ratios of the gels in the presence of microsphere were not high even just beyond the gel points, suggesting a preferential incorporation of microsphere into the gel. These are discussed mechanistically.

Copolymerization of Poly(allyl methacrylate) Crosslinked Polymer Microspheres with Allyl Benzoate

“…The gel point was estimated to be 23.0% for the copolymerization of ABz with 18 wt% of IV; obviously, the gelation was promoted with decreased particle size, in contrast with the case that no gelation occurred for 18 wt% of I. These are in line with our previous discussion 1 that the gelation is observed only under the polymerization condition in which the PAMA microspheres collide each other.…”

“…Here it is worthy to note that in the preceding article, 1 PAMA microsphere I is copolymerized with ABz as compared to its copolymerization with DAT. Thus, for the copolymerization of ABz with 9.1 wt% of I no gelation is observed even at 43.6% conversion, while gelation occurs at 27.5% in the case of DAT.…”

“…In the preceding article, 1 we have discussed in detail the crosslinking polymerization of diallyl terephthalate (DAT) in the presence of microgel-like poly(allyl methacrylate) microsphere (PAMA microsphere) with abundant pendant allyl groups in order to clarify the polymerization behavior of microgel in the free-radical crosslinking polymerization of multivinyl compounds 2 and, moreover, the reactivity of crosslinked polymer microspheres. In the presence of a small amount of microsphere the wide, free space among microspheres is a main polymerization locus of DAT and, concurrently, a small portion of DAT copolymerizes with the allyl groups present on the surface of microsphere.…”

Delayed gelation through chain-transfer reactions: Mechanism for stress reduction In methacrylate networks

“…It is important to note that this approach differs completely from the proposed soft-start polymerization protocols [13, 14] as a means to delay gelation with respect to time rather than conversion. While extending the time to reach the gel point, the use of an initially low irradiance photocuring protocol actually increases chain lengths and leads to gelation at a lower conversion value than would be obtained at higher radical concentrations at higher levels of irradiance [15]. …”

Structural Analysis and Mechanical Characterization of Hyaluronic Acid-Based Doubly Cross-Linked Networks

“…Therefore, they are not very useful for tissue engineering applications. Hydrogels with HGPs as the effective cross-linkers , may provide tailored viscoelasticity and structural integrity and are suitable for use as injectable materials for soft tissue regeneration.…”