Interfacial Polycondensation Synthesis of Optically Sensitive Polyurea Microcapsule

Abstract

TMPTA prepolymer resin and photoinitiators of ITX/TPO had been encapsulated in core-shell structured microcapsules as optical responding ingredients based on interfacial polycondensation method, and polyurea structured microcapsule shell had been formed on the sheared O/W interface. The synthesized microcapsule had regular core-shell structure with the diameter of about 0.455 μm and shell thickness of about 40 nm. UV-visible absorption spectra indicated that the encapsulated ITX and TPO photoinitiators could efficiently absorb UV irradiation. Under exposure, the C=C bonds absorbance of the microencapsulated TMPTA decreased rapidly and then nearly unchanged during further exposure after 30 s. This implied that the optical response was achieved by C=C bond cleavage of TMPTA monomer initiated by the photoinitiator radicals, to form network polymers in microcapsules. The relative crosslinking rate was about 50%. Due to core polymer formation, the thermal phase change temperature of exposed microcapsules was narrowed and ranged from 105 to 205°C, compared with that from 125 to 260°C of unexposed microcapsules. Furthermore, the image density decrease at longer irradiation time had also verified the optical responding function of the synthesized microcapsules in macroscopic viewpoint.

UV-Light Curing of 3D Printing Inks from Vegetable Oils for Stereolithography

“…All characteristic peaks of groups present in AESO corresponding to (-OH) stretching vibrations of (C=O) and (C-O) ester groups are present before and after the UV exposure in all spectra at 3462, 1733 and 1219, and 1271 cm −1 , respectively [ 39 ]. The bands corresponding to the asymmetric stretching of (O=C-O) at 1361 cm −1 [ 40 , 41 ] and stretching vibrations of ester (C-O-C) at 1158 cm −1 were also observed [ 39 ]. For AESO 3 resin, upon UV-irradiation, a decrease of the intensity is observed in (CH 2 =CH-R) scissioning and (C=C) at 1406 and 1632 cm −1 , respectively.…”

“…For AESO 3 resin, upon UV-irradiation, a decrease of the intensity is observed in (CH 2 =CH-R) scissioning and (C=C) at 1406 and 1632 cm −1 , respectively. These decreases during the UV-irradiation happen because (C=C) bonds in acrylate groups are destroyed by the initiation of radicals and the occurrence of the crosslinking [ 36 , 40 , 42 , 43 ]. Additional conformation of acrylate polymer vinyl functionality is characterized by the (CH 2 =CH (CO)-O-) vinyl group at 985 cm −1 , which also decreases upon UV-irradiation [ 40 ].…”

“…These decreases during the UV-irradiation happen because (C=C) bonds in acrylate groups are destroyed by the initiation of radicals and the occurrence of the crosslinking [ 36 , 40 , 42 , 43 ]. Additional conformation of acrylate polymer vinyl functionality is characterized by the (CH 2 =CH (CO)-O-) vinyl group at 985 cm −1 , which also decreases upon UV-irradiation [ 40 ]. The decrease of the later peak affects also the peak at 1733 cm −1 related to the (C-O) of the ester groups, which is due to the electronic conjugation.…”

Visible-Light-Initiated Free-Radical Polymerization by Homomolecular Triplet-Triplet Annihilation

“…67 Since a C=C bond is consumed during polymerization, the progress of gel formation was monitored (Table S1) using its characteristic vibration at 1,635 cm À1 in the TMPTA IR spectrum. 68 With IR spectra normalized to the C=O band at 1,725 cm À1 , 69 the absorbance of the C=C bonds at 1,635 cm À1 decreases with increasing 427 nm exposure time, indicating that the TMPTA monomer is being consumed as a result of S 2 photoactivation, Figure 4.…”

Visible-Light Initiated Free Radical Polymerization by Homomolecular Triplet-Triplet Annihilation

“…66 Since a C=C bond is consumed during polymerization, the progress of gel formation was monitored (Table S1) using its characteristic vibration at 1635 cm −1 in the TMPTA IR spectrum. 68 With IR spectra normalized to the C=O band at 1725 cm -1 , 69 the absorbance of the C=C bonds at 1635 cm -1 decreases with increasing 427 nm exposure time, indicating that the TMPTA monomer is being consumed as a result of S2 photoactivation, Figure 4.…”