Microfluidic Fabrication of Morphology-Controlled Polymeric Microspheres of Blends of Poly(4-butyltriphenylamine) and Poly(methyl methacrylate)

Abstract

Multicomponent polymer particles with specific morphology are promising materials exhibiting novel functionality which cannot be obtained with single-component polymer particles. Particularly, the preparation of such kinds of polymer particles involving electrically or optically active conjugated polymers with uniform size is a challenging subject due to their intense demands. Here, microspheres of binary polymer blend consisting of poly(4-butyltriphenylamine) (PBTPA)/poly(methyl methacrylate) (PMMA) (1:1 in weight) were produced via a microfluidic emulsification with a Y-shaped microreactor, and a subsequent solvent evaporation method. The flow rate of the dispersed phase (polymer solution) was fixed to 7 µL/min, and 140 or 700 µL/min of the flow rate of the continuous phase (aqueous 0.6 wt % of poly(vinyl alcohol) (PVA) solution) was utilized to produce the dispersion with different diameter. The concentration of dispersed phase was adjusted to 0.1 or 1.0 w/v%. Core-shell, Janus and dumbbell type microspheres were obtained dependent on the flow rate of continuous phase. Incomplete core-shell type microspheres were produced for the blend involving low molecular weight PMMA. Complex Janus and core-shell type microspheres were fabricated by the addition of sodium dodecyl sulfate (SDS) to continuous phase. It is found that final morphologies are strongly dependent on the initial conditions of dispersion including the particle size suggesting that the morphologies are governed by the kinetical factors together with the conventionally accepted thermodynamic ones.

Keywords: microfluidic; microreactor; microsphere; morphology; poly(4-butyltriphenylamine); polymer blend.

Figure 1

Schematic illustration of procedures to produce microspheres by combining microfluidic emulsification and solvent evaporation.

Figure 2

SEM images of microspheres of PBTPA/PMMA prepared with the conditions listed in Table 1 (A1, B1, B2, C1 and C2), (a) as-prepared, (b) after soaking with acetone, (c) schematic models.

Figure 3

SEM images of microspheres of PBTPA/PMMA prepared with the conditions listed in Table 1 (A2 and A3), (a) as-prepared, (b) cracked, (c) after soaking with acetone, (d) schematic models.

Figure 4

Plausible temporal evolution of phase separated morphology for PBTPA/PMMA composite microsphere (a) B1, (b) C1, (c) A1, red: PBTPA, blue: PMMA.

Figure 5

Formation of surface morphology of microspheres of PBTPA/PMMA blend (the surface consists mainly of (a) PMMA-rich phase, (b) PBTPA-rich phase).

Figure 6

Illustration of the effect of molecular weight of PMMA in the formation of PBTPA/PMMA composite microsphere.

Figure 7

Illustration of the effect of SDS in the formation of PBTPA/PMMA composite microsphere.