Abstract
Various spherulites or spherulitic crystals are widely encountered in polymeric materials when crystallized from viscous melts or concentrated solutions. However, the microstructures and growth processes are quite complicated and remain unclear and, thus, the formation mechanisms are rather elusive. Here, diverse kinds of spherulitic growths and patterns of typical polyesters via evaporative crystallization of solution-cast thin films are delineated after detailed investigating the microstructures and in situ following the developing processes. The spherulitic crystals produced under different evaporation conditions reflect variously optical features, such as the usual Maltese Cross, non-birefringent or half-birefringent concentric-rings, extinction spiral banding, and even a nested ring-banded pattern. Polymer spherulites are composed of stacks of radial fibrillar lamellae, and the diversity of bewitchingly spherulitic morphologies is dominated by the arrangement and organization of radial lamellae, which is predicted to be tunable by modulating the evaporative crystallization processes. The emergence of various types of spherulitic morphologies of the same polymer is attributed to a precise manipulation of the radial lamellar organization by a coupling of structural features and specific crystal evolving courses under confined evaporation environments. The present findings improve dramatically the understanding of the structural development and crystallization mechanism for emergence of diverse polymer spherulitic morphologies.
Highlights
Since the first observation of ordered crystals in high polymers there has been a vast amount of scientific activity and longstanding interest in the study of polymer crystallization and morphology, for which is it a basic and significant research field in polymer physics but it exerts profound influence on material properties and performances [1,2,3,4]
It has been illustrated that a long-range mass transfer is necessary for rhythmic crystallization. It is evident from in situ optical microscopy (OM) images (e.g., Figure 13c–i) that the repetitively-altered Newton interference rings ahead of the growing crystal front that are indicative of the generation of interference rings ahead of the growing crystal front that are indicative of the generation of evaporative evaporative convection are a common presence for the formation of concentric ringed spherulites from evaporative crystallization of solution-cast films [47]
Polymer spherulites possess the unique structural feature of being composed of a summary, polymercrystals spherulites possess the unique structural of being composed of largeIn amount of lamellar that elongate in the radial directionfeature synchronously, and diverse a large amount of lamellarofcrystals that elongate inPEA
Summary
Since the first observation of ordered crystals in high polymers there has been a vast amount of scientific activity and longstanding interest in the study of polymer crystallization and morphology, for which is it a basic and significant research field in polymer physics but it exerts profound influence on material properties and performances [1,2,3,4]. An theorigin non-birefringent structural discontinuity deriving from an alternative stacking of lamellar crystals and the blended concentric-ringed spherulites (ZBCRS) of isotactic polystyrene (iPS), respectively [33,34] It should amorphous materials [35,36,37].banded. It is well known that the morphology of and modulate the morphological behavior of polymer spherulitic growths from a unified standpoint crystalline polymers is determined by the chain and crystal structures (the internal of manipulating lamellar arrangement theofradial growth(the direction during features), butthe by the organization crystallization and condition and the along process that growth external factors). The subscript in each polymer abbreviation indicates its number average molecular weight
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