Interplay between Crystallization and Entanglements in the Amorphous Phase of the Crystal-Fixed Polymer Poly(ϵ-caprolactone)

Kurz, Ricardo; Schulz, Manfred; Scheliga, Felix; Men, Yongfeng; Seidlitz, Anne; Thurn‐Albrecht, Thomas; Saalwächter, Kay

doi:10.1021/acs.macromol.8b00809

Cited by 54 publications

(67 citation statements)

References 67 publications

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“…Wang et al characterized the entanglement state of iPP by rheological testing, and then studied the crystallization behavior of iPP-disentangled melt [ 35 ]. R. Kurz et al also related the entanglement in the melt to the entanglement in the amorphous zone; their experimental results suggest that entanglement controls the thickness of the amorphous zone [ 36 ]. Recently, Men et al revealed the decisive role of entanglements in the transition between the α and tetragonal crystal form of Polybutene-1 [ 30 ].…”

Section: Resultsmentioning

confidence: 99%

Investigation on the α/δ Crystal Transition of Poly(l-lactic Acid) with Different Molecular Weights

2021

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Poly(l-lactic acid) (PLLA) crystal possesses a complex polymorphism, and the formation mechanism of various crystal forms has been a hot research topic in the field of polymer condensate matter. In this research, five kinds of PLLA with different molecular weights were prepared by ring-opening polymerization with strict dehydration operations and multistep purification treatments. Then, thin film isothermal crystallization experiments were carried out to obtain crystallized samples. Previous research has proven that the PLLA α crystal form is usually formed at a temperature above 120 °C and the PLLA δ (or α’) crystal form is usually formed at a temperature below 120 °C. However, in this research, the characterization results indicated that the PLLA crystal changed from δ form to α form with the decrease of molecular weight at a temperature of 80 °C. Considering the molecular weight effect, the paper argued that the transitions of the α/δ crystal form are not only associated with temperature, but also related to entanglement state before crystallization. The small-angle X-ray scattering of the PLLA crystal and rheology analysis of the PLLA melt before crystallization further proved the significant role of entanglement. Finally, we tentatively proposed the entanglement effect mechanism on the transitions of the α/δ crystal form.

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Section: Resultsmentioning

confidence: 99%

Investigation on the α/δ Crystal Transition of Poly(l-lactic Acid) with Different Molecular Weights

2021

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“…Generally, the melt viscosity is considered to be highly related to the molecular weight of a polymer due to the chain entanglements. 48,49 In our case, the molecular weight level of all coPA6 was close, indicating that the difference in melt viscosity was highly dependent on material characteristics. 50 However, the high melt viscosity in PA6 B1 and PA6 B2 indicated that the trace-content BAHT-AA loading in the PA6 backbone can enhance the intermolecular interaction by π-π stacking of the aromatic ring.…”

Section: Tensile Properties and Water Absorptionmentioning

confidence: 49%

Synthesis and characterization of trace aromatic copolyamide 6 with tunable mechanical and viscoelastic behavior

Chen

Lee

Rwei

2021

J of Applied Polymer Sci

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terephthalamide/adipic acid (BAHT-AA) was chosen to be used as a comonomer to develop a novel polyamide 6 (PA6) with the trace-content aromatic structure. A series of polyamide 6 copolymers (coPA6) with trace BAHT-AA loading were synthesized to yield the modified copolyamides with multiple interactions of hydrogen bonding and π-π stacking on the PA6 backbone. It was proved that the thermal stability and mechanical properties of coPA6 were significantly enhanced because of the introduction of the trace BAHT-AA segment. More importantly, adding a trace (1, 2, and 4 mole%) of BAHT-AA could effectively increase the network structure and highly decrease the free volume fraction in the polymer system that is proved by the relaxation behavior and melt viscoelastic behavior. The results showed that the integrated performances of coPA6 were better than that of pure PA6, which was highly correlated with the aforementioned multiple interactions. For example, outstanding tensile strength (73.0 vs. 56.8 MPa), and modulus (1167 vs. 929 MPa), and so on. This work provided the traditional PA6 with the modification of outstanding mechanical and thermal performances, thus expanding its application for the plastics and textile industries.

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“…In a model suggested by Men and coworkers, a semicrystalline polymer is considered as a composite of two interpenetrating networks between interconnected lamellae blocks and the entangled amorphous network . The critical aspects of the true stress‐strain curves of such polymers include, local intralamellar slip processes just before yield and after a purely elastic deformation (point A), and a change into a collective activity of slip motions all over the lamellae at the yield point of the polymer (point B). On further strain, lamellae disaggregation and chain unfolding (also referred to as mechanical melting) and recrystallization into fibrillar structures occur (point C) .…”

Section: Resultsmentioning

confidence: 99%

Effect of melt miscibility, polymorphism, and crystal morphology on tensile deformation of blends of isotactic polypropylene and propylene‐1‐hexene random copolymers

Janani

Alamo

2020

Polymer Crystallization

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The ductile behavior of isotactic polypropylene (iPP) can be effectively increased by blending with small contents (<25%) of a random propylene 1-hexene copolymer (PH). In this work, we have studied the uniaxial tensile deformation of binary blends of iPP with PH copolymers with 11 or 21 mol% 1-hexene. Blends iPP/PH11 are melt-miscible in the whole range of composition while iPP/PH21 blends are meltimmiscible, but partially compatible. On cooling, the lamellar morphology of each type of blend differs accordingly, and impacts their mechanical deformation. Miscible iPP/PH11 blends develop inter-mixed monoclinic lamellar stacks interconnected by tie molecules of iPP and PH admixed in the amorphous phase. During deformation, the monoclinic crystals transform to oriented mesophase at low strains due to effective stress transfer through the interconnected topology. These blends display the largest strain (~800%) and low recovery. Conversely, immiscible iPP/PH21 develop a coarser morphology of monoclinic and trigonal crystallites in the iPP-rich and PH21-rich domains, respectively. Less effective stress transfer associated with the coarse iPP/PH21 morphology leads to a delayed onset of orientation and a less effective monoclinic-mesophase transformation. The PH21 trigonal crystals of the blend orient but do not undergo polymorphic transformation. At high elongations fibrillar strain-induced trigonal crystals, provide a network of stable physical junction points that relax to the random orientation upon removal of the load, thus enhancing the elastic recovery of iPP/PH21 blends. K E Y W O R D S iPP copolymers, iPP crystallization, iPP mechanical properties, iPP polymorphism 1 | INTRODUCTION The polymorphic behavior, semicrystalline structure, and mechanical properties of isotactic poly(propylene) (iPP) change when defects or a comonomer are incorporated to the chain. The addition of a suitable content of comonomer to the iPP chain enables polypropylene materials with a wide spectrum of properties ranging from rigid thermoplastics to elasto-plastomers or to elastomers. [1]Mixtures of iPP and propylene-1-alkene thermoplastic elastomers, form both miscible, and immiscible (but compatible) blends. [2][3][4] In binary blends of random atactic propylene-butene (PB) copolymers analyzed by SANS, the melt-miscibility increased with increasing difference in content of 1-butene. [5] This effect was attributed to a negative enthalpy interaction between propylene and 1-butene monomer units and to attractive entropic contributions. Based on such results, it was hypothesized that the branches longer than ethyl,

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Interplay between Crystallization and Entanglements in the Amorphous Phase of the Crystal-Fixed Polymer Poly(ϵ-caprolactone)

Cited by 54 publications

References 67 publications

Investigation on the α/δ Crystal Transition of Poly(l-lactic Acid) with Different Molecular Weights

Investigation on the α/δ Crystal Transition of Poly(l-lactic Acid) with Different Molecular Weights

Synthesis and characterization of trace aromatic copolyamide 6 with tunable mechanical and viscoelastic behavior

Effect of melt miscibility, polymorphism, and crystal morphology on tensile deformation of blends of isotactic polypropylene and propylene‐1‐hexene random copolymers

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