Phase diagram showing lowering of the melting temperature of the crystalline PEO upon blending with the photoreactive DA monomer. Nonequilibrium snapshots of the coexistence curves were calculated at each conversion of DA monomer into the polymer subjected to photopolymerization. Various parameters used for the calculation of the phase diagram of PEO/DA blends were , , , , and at .
Directional crystal growth showing seaweed growth from the frame and dense branching morphology (or spherulites) in the bulk: (a) the crystal order parameter field and (b) the corresponding composition order parameter field following PIC under a linear gradient illuminating beam. Note that the intensity of illuminating beam is the lowest at the left and highest on the right side . The frame of the calculated patterns corresponds to the square grid of . The dimensionless parameters used in this dynamic calculation along with the materials parameters were listed in Table I.
Dynamic calculations carried out under a circular light intensity profile. The sharp transition of the interface from the high intensity to low intensity interface region leads to directional crystal growth toward the high intensity center and no crystal growth was observable in the dark region due to the lack of the photoreaction. The last picture at the bottom right shows the observed morphology of the 30/70 PEO/DA blend, showing directional crystal growth under the polarized optical microscopic view. The computed picture frame corresponds to .
Dynamic calculations carried out under a smooth Gaussian intensity profile revealed a faster growth in the high intensity core region vs slower growth in the low intensity region in the outer area. The entire view area was filled with dense branching morphology (or spherulites) as they grew in the entire domain as the monomer was converted in to polymer. The last picture at the bottom row shows the optical micrograph of the emerged spherulitic morphology from the 30/70 blend of PEO/DA. The light intensity has a Gaussian profile after passing through a set of convex lens. The computed picture frame corresponds to .
Dynamic calculations carried out under a sharper Gaussian intensity profile showing crystallization in the high intensity region and directional crystal growth from the low intensity region toward the core of high intensity region. The last picture at the bottom row shows the optical micrograph of the emerged spherulitic morphology from the 30/70 blend of PEO/DA. The computed grid corresponds to .
Comparison among crystallization in polymer blends undergoing polymerization when exposed to circular, slowly decaying Gaussian profile and a sharp Gaussian profile. Note that the directional crystal growth is dependent on the intensity profile and the sharp Gaussian profile is an intermediate between the circular profile having sharp interface in which the growth advances directionally toward the high intensity region, as opposed to the gradual smooth Gaussian profile in which crystals grow away from the high intensity core. The computed picture frame corresponds to .
Experimental and materials parameters of PEO/DA blends and the corresponding dimensionless model parameters used in the numerical computations.
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