A modulated differential scanning calorimetry and small-angle x-ray scattering study of the interfacial region in structured latices

Abstract

A interface de latexes de poliestireno (PS)-poliacrilato de metila (PMA) foi investigada por calorimetria diferencial de varredura no modo modulado (DSC-modulado) e por espalhamento de raios-x de baixo ângulo (SAXS). A fração em massa da interface destes latexes foi estimada através do sinal do DSC-modulado, dCp/dt. Foi encontrado o valor de 13% para latexes de PS-PMA (1:1 em massa) contendo PS reticulado com diferentes densidades de reticulação (0, 1, 3, 5 e 10 mol% de agente reticulante). O aumento da densidade de reticulação não alterou de forma significativa a fração da interface. O modelo core-shell foi usado na análise dos dados de SAXS. Os dados de DSC-modulado forneceram informações apenas sobre a fração em massa da interface, entretanto a combinação das técnicas DSC-modulado e SAXS forneceu informações adicionais sobre a morfologia dos latexes.The interfacial structure of poly(styrene) (PS)-poly(methyl acrylate) (PMA) structured latices has been investigated by means of modulated-temperature differential scanning calorimetry (M-TDSC) and small-angle x-ray scattering (SAXS). The differential of heat capacity, dCp/dT, signal from M-TDSC was used to quantify the weight fraction of interface in these latices. For PS-PMA (50:50 by weight) structured latices in which the PS component had different crosslink densities (0, 1, 3, 5 and 10 mol% of crosslinking agent), the weight fraction of interface was about 13%. With increasing crosslink density, the fraction of interface increased only slightly. A core-shell model has been used to analyse SAXS data for these PS-PMA latices. M-TDSC can only provide information about the weight fraction of interface, but the combination of M-TDSC and SAXS can provide much more information on the morphology of such structured latices.

Measuring the extent of phase separation during polymerization of composite latex particles using modulated temperature DSC

“…Modulated DSC has been shown to be very useful to quantify the amount of polymer present within interfacial regions in polymer blends15–17 as well as to monitor the extent of phase separation during polymerization reactions 18. In fact, Karlsson et al used both DSC and dynamic mechanical analysis (DMA) to study the amount of interphase and the mechanical properties of films derived from both composite latices and from latex blends 19.…”

“…In fact, Karlsson et al used both DSC and dynamic mechanical analysis (DMA) to study the amount of interphase and the mechanical properties of films derived from both composite latices and from latex blends 19. One straightforward approach15–17 is to compare the value of the Δ C p at the glass transitions to the values expected for the corresponding pure polymers. It is often found that the Δ C p in a composite is less than expected, and the difference is attributed to polymer that is present within the polymer/polymer interfacial zones.…”

Characterization methods of polymer core–shell particles

“…MDSC was used to investigate the effect of the cross-link density of a polystyrene seed on the thickness of the interfacial region in the polystyrene/poly(methyl acrylate) (PS/PMA) particles synthesized by seeded polymerization [84]. The weight fraction of interfacial region was evaluated on the basis of depletion of dCp/dT for PS/PMA compared to dCp/dT values for pure components.…”

Nonequilibrium morphology development in seeded emulsion polymerization. IV. Influence of chain transfer agent

“…The second system used a seed polymer of poly(butyl acrylate‐ co ‐St) [P(BA‐ co ‐St)] with MMA as the second‐stage monomer, representing a CS system. The MWDs of the resulting second‐stage polymers were determined using gel permeation chromatography (GPC) and the morphologies of the composite particles were characterized using transmission electron microscopy (TEM), differential scanning calorimetry (DSC),15, 30–33 and surfactant titration 34–37…”