The effect of temperature and annealing on the phase composition, molecular mobility and the thickness of domains in high-density polyethylene

Morphology of Novel PEAs Containing Two Consecutive Amide Bonds Randomly Distributed Along the Polyester Backbone

“…Therefore, at temperatures above the T g it is possible to discriminate between the various phases by proton NMR measurements performed without MAS. [24,30] However, the crystallinity values extracted by NMR generally differ from those obtained by other methods for different reasons: (i) the crystalline and amorphous phases are discriminated on the basis of different properties, such as the enthalpy of melting in DSC and chain mobilities in NMR. (ii) The simplified two-phase model often is not the most appropriate way to describe the morphology of semi-crystalline polymers due to the presence of a crystalline-amorphous interface.…”

“…However, very often, the morphology of such materials is much more complex and the existence of an interface between the two phases was reported. [23,24] In the last decades, the importance of such interfacial region received particular attention as it affects not only the thermal but also the mechanical properties of the material. [25,26] Therefore, detailed knowledge of the microscopic properties in terms of the degree of crystallinity, phase composition, chain dynamics and domain sizes is required in order to customise the macroscopic properties of the material.…”

“…In particular, it can probe the microphase separation and extract domain thickness with the help of spin diffusion experiments. This type of experiment, in which the proton magnetisation is selectively suppressed in one of the phases with the help of dipolar filters [27][28][29][30] and then allowed to equilibrate by means of dipolar-mediated flip-flop process was successfully applied to various types of solid polymers including polyolefins, [24] nylon fibres [29,30] and block copolymers, [29][30][31][32] but also to much more complex systems such as confined biomolecules. [33] Generally, the domain sizes estimated by the proton spin diffusion agree very well with those estimated by X-ray diffraction.…”

“…[33] Generally, the domain sizes estimated by the proton spin diffusion agree very well with those estimated by X-ray diffraction. [24] In the case of PEAs, Serrano et al applied various 13 C solidstate NMR techniques to study the morphology of alternating PEAs. [34] They showed that the length of the spacer has significant impact on the molecular dynamics.…”

“…On the other hand, proton NMR gained significance as a reliable tool for the characterisation of multiphase polymer materials, even for those with complex morphologies as long as sufficient molecular mobility exists between the different phases in order to discriminate them. [24,29,30] Proton NMR benefits from high sensitivity which translates into short measuring time and from simplicity in performing the experiments without the need of expensive and complicated NMR probes.…”