Crystallization and Morphology of Immiscible Double Crystalline Poly(p-dioxanone)–Poly(tetramethylene ether)glycol Multiblock Co-polymers

Abstract

The crystallization behavior and intriguing crystal morphologies of double crystalline poly(p-dioxanone)-poly-(tetramethylene ether)glycol (PPDO−PTMEG) multiblock co-polymers were investigated via differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and transmission electron microscopy (TEM). The effects of composition and microphase morphology on the crystallization of each segment were also explored. The results indicated that PPDO segments and PTMEG segments were immiscible. Composition and unique microphase morphology affected the crystallization ability and crystal morphology of PPDO and PTMEG segments. The kinetics of isothermal crystallization was studied calorimetrically and microscopically. It was found that crystallization rate of PPDO segment was slower than that of PPDO-H, which should be responsible for the dilution of PTMEG segments. In the case of PTMEG segments, the crystallization kinetics were highly correlated with the microphase morphology. ■ INTRODUCTIONBlock co-polymers involve a wide variety of polymeric material, which has one type of repeat unit joined to another repeat unit at one or both ends. 1−5 Compared to its parent polymer, this spaced chain structure of block co-polymer make it show significant difference in properties, such as crystallization behaviors. 6−10 Depending on the segregation strength in the melt, either crystallization can drive structure formation for miscible systems as well as some weakly segregated co-polymers, or crystallization can be confined within the segregated microdomain for immiscible systems with strongly segregated co-polymers. So the block co-polymer that involves at least one crystalline polymer has attracted great interest for their crystallization behaviors and crystalline morphologies. 10−15 In double crystalline block co-polymers, the situation is even more complicated. 1,3,13,16−22 When cooling from the melt, both of the blocks can crystallize at different temperatures within different crystallization times: one crystallized block can produce a specific morphology and affect the crystallization and morphology of another. 11,23 If the difference in melting temperature between the two segments is large enough, intriguing crystallization morphologies may occur. 3,16,24 Therefore, the crystallization condition plays an important role in the crystallization behavior of double crystallization co-polymers. Besides, the miscibility of the two segments also affects the crystallization process. For the miscible double crystalline co-polymer, spherulites of one segment continue to grow in those of the other segment when they are crystallized from a homogeneous melt; also, the difference in the melting temperature between the two segments can influence the formation process. In the case of a small difference in T m , both segments develop spherulites simultaneously; however, when the difference is an intermediate value, the spherulites of the higher-T m segment first fill the entire volume, and the lower-T m segment then nucleates an...

Poly(ether ester) and related block copolymers via organocatalytic ring‐opening polymerization

“…Compared with the DSC curves of PPDO and PCL homopolymers, the melting points for the PCL segment of the block polymers were slightly reduced from 56.8 °C to 53.0 °C with the PDO unit content varying from 0 to 78 mol%, while the T m for the PPDO segment ranged from 101.4 °C to 107.5 °C with the ε‐ CL unit content varying from 0 to 55 mol%. The independent melting point peaks throughout the composition range indicate PDO and CL cannot co‐crystallize 55–58 . Table 2 also presents the enthalpy of fusion of each constituent and the degree of crystallinity (X c ) calculated with those values once they have been normalized by the composition.…”

“…53,54 As shown in Figure 4A and PDO and CL cannot co-crystallize. [55][56][57][58] Table 2 also presents the enthalpy of fusion of each constituent and the degree of crystallinity (X c ) calculated with those values once they have been normalized by the composition.…”