posted on 2021-09-29, 15:34authored byChuyi Liao, Xiaogong Wang
This
work investigated a unique type of triphasic colloidal particles
composed of an azo polymer (PCNAZO), a fluorescent pyrene-containing
polymer [P(MMA-co-PyMA)], and a poly(dimethylsiloxane)-based
polymer (H2pdca-PDMS), focusing on the synthesis, forming
mechanism, morphology control, and functions. The triphasic particles
with well-defined morphologies were assembled through the microphase
separation of the components in dichloromethane (DCM) droplets in
an aqueous medium, induced by the gradual evaporation of the organic
solvent. The real-time fluorescence emission spectra of the pyrenyl
moieties and in situ microscopic observations show
that the formation of the triphasic particles undergoes the segregation
of the PCNAZO-rich phase, separation between P(MMA-co-PyMA)-rich and H2pdca-PDMS-rich phases, coalescence,
and solidification in the dispersed droplets. The structure formation
is due to the strong phase separation of the polymers as revealed
by the calculations based on the Flory–Huggins theory. The
morphologies and phase boundaries of the particles are found to be
controlled by the interfacial energy between the phases and processing
conditions. The triphasic particles thus obtained possess a series
of interesting functions stemming from the polymers and the triple-compartmentalized
structures. After being deposited on a substrate, the H2pdca-PDMS parts can tightly adhere on the surface, caused by the
spreading nature of the polymer when slightly swelled by DCM. Upon
irradiation with a linearly polarized laser beam at 488 nm, the azo
polymer compartments show a significant elongation along the electric
vibration direction of the polarized light, accompanied by the cooperative
deformation of the H2pdca-PDMS pads. When dispersed in
water and adhered on the substrate surface, the triphasic particles
exhibit tunable colors originating from the fluorescence of the pyrenyl
fluorophores and light absorption of the azo chromophores. The real-time
investigation methods developed here could lead to the deep understanding
of the structure formation process in the confined volume and be applied
in phase-separation study of other polymers as well.