Control of Polymer Properties by Entanglement: A Review

Abstract

Chain entanglement, either cohesional or topological, distinguishes polymers from other engineering materials. It impedes the movement of molecular segments and influences the polymer rheology, morphology, and mechanical properties. Although a high level of entanglement can increase the polymer toughness, excessive entanglement should be avoided because it causes a high melt viscosity making the processing difficult. This review tended to elucidate the influence of entanglement on the polymer structure, determining the material properties and processability. A wide range of methods used to fine control the degrees of chain entanglement are summarized. The methods are applicable to polymers in solutions, melts, and condensed states with advantages and limitations discussed in detail. The authors also examined the effect of the entanglement on polymer crystallization—the mechanism remains a controversial issue. This review will provide general guidance to designing and processing polymer materials with desired properties via a rational route of controlling the chain entanglement.

Interfacial Friction Controls the Motion of Confined Polymers in the Pores of Nanoparticle Packings

“…The absence of reptation scaling suggests that the role of topological entanglements in the motion of the chains is significantly reduced. This can be seen as indirect evidence of disentanglement under confinement as can be seen in previous studies involving the capillary rise of polymeric liquids ,,− and mechanical properties of composites. − It should be pointed out that the MWs we use to extract the Rouse-like scaling exponent is narrow (25k–50k MW) due to the experimental limitation of loading higher MW PDMS into gels. The critical MW at which polymer dynamics start to be impacted by entanglement ( M c ) in the bulk is ∼2.5 times the entanglement molar mass ( M e ), which gives M c = 30,000 for PDMS ( M e = 12,000 g/mol).…”

Optical-Tweezers-integrating-Differential-Dynamic-Microscopy maps the spatiotemporal propagation of nonlinear strains in polymer blends and composites

“…This mechanism, consistent with Fig. 2c, should become stronger as _ γ increases, until it is faster than the entanglement rate υ e , i.e., the rate for each entanglement segment to 'feel' its tube confinement from surrounding entangling polymers 1,62,78,79 .…”

Synthesis of UV-curable polyurethane-acrylate hybrids with tuneable hardness and viscoelastic properties on-demand

“…The temperature increase in T b can be explained by the reduction in the polymer's chain mobility due to an increase of crosslinking points as the acrylate wt% is increased. These samples with lower acrylate wt% inherently possess a higher number of freely moving polymer chains that cause more internal frictions or entanglement constrains among chains 44 and subsequently, these polymers have a higher energy dissipation capability (higher tan d peak). 45 In parallel, the increase in the crosslinking density associated with the higher acrylate wt% produces a widening of the tan d peak due to a greater heterogeneity in the average length between crosslinking points.…”

“…While having a similar cross-linking density with the same acrylate wt%, in PEGMA PUA, the longer polymer chains allow for more freedom of movements and an increased length for entanglement interactions. 44 This increased interaction among the molecules is translated directly into an increased viscous behaviour.…”