Direct and indirect effects on molecular mobility in renewable polylactide–poly(propylene adipate) block copolymers as studied <i>via</i> dielectric spectroscopy and calorimetry

Klonos, Panagiotis Α.; Terzopoulou, Zoi; Zamboulis, Alexandra; Valera, Miguel Ángel; Mangas, Ana; Kyritsis, Apostolos; Pissis, P.; Bikiaris, Dimitrios N.

doi:10.1039/d2sm00261b

Cited by 13 publications

(30 citation statements)

References 87 publications

(166 reference statements)

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“…The surprising effect is the further lowering of T g with the implementation of crystallinity, as, conversely, the presence of crystals would be expected to hinder the polymer chains diffusion and, subsequently, to elevate the T g [ 16 , 49 , 50 , 51 ] (and references therein). So far, these results confirm previous recordings on the same systems [ 26 ], which actually generated the interest for the present ‘follow-up’ study.…”

Section: Resultssupporting

confidence: 90%

“…The drop in T g of PLA by the addition of PPAd on the same polymer chain was rationalized in terms of the plasticization effect of the small PPAd blocks. The effect is also facilitated by the overall shortening of the copolymer chains [ 26 ]. The surprising effect is the further lowering of T g with the implementation of crystallinity, as, conversely, the presence of crystals would be expected to hinder the polymer chains diffusion and, subsequently, to elevate the T g [ 16 , 49 , 50 , 51 ] (and references therein).…”

Section: Resultsmentioning

confidence: 99%

“…To be more precise, the crystalline fraction, CF, as well as the semicrystalline morphology, the crystals’ dense or sparce distribution and the number/size/density of the crystallites, are the key parameters [ 21 , 22 , 23 , 24 ]. Strongly connected to the crystallinity, nucleation and crystal growth is the mobility of PLA chains, more precisely, the diffusion capability of the chains (cooperativity, chain–chain entanglements) and folding (chain rigidity) [ 25 , 26 ].…”

Section: Introductionmentioning

confidence: 99%

“…In addition, the polar terminal groups of PnAAd (mainly −OH) favor the use of PnAAd as initiators for the ROP of PLA [ 30 ], which is quite convenient from the chemistry point of view, both from the laboratory as well as the upper-scale production. In particular, the low T g and the relatively flexible polymer chain make these polyesters good candidates to serve as ‘plasticizers’ for PLA [ 26 , 30 , 31 , 32 , 33 ], resulting in, among other outcomes, the improvement of the biodegradation and compostability of the PLA/PnAAd systems (copolymers and blends).…”

Section: Introductionmentioning

confidence: 99%

“…The present article reports a more ‘basic research’-targeted investigation. In our recent work on diblock copolymers with poly(propylene adipate) (PPAd) and PLA forming the two blocks [ 26 ], we recorded interesting and non-trivial findings with respect to molecular mobility. We recorded that in the amorphous state, the increase in the PPAd fraction led to an expected lowering of T g , whereas, strikingly, the involvement of non-isothermal crystallization resulted in a further suppression of T g (even below 0 °C).…”

Section: Introductionmentioning

confidence: 99%

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Revisiting Non-Conventional Crystallinity-Induced Effects on Molecular Mobility in Sustainable Diblock Copolymers of Poly(propylene adipate) and Polylactide

et al. 2022

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This work deals with molecular mobility in renewable block copolymers based on polylactide (PLA) and poly(propylene adipate) (PPAd). In particular, we assess non-trivial effects on the mobility arising from the implementation of crystallization. Differential scanning calorimetry, polarized light microscopy and broadband dielectric spectroscopy were employed in combination for this study. The materials were subjected to various thermal treatments aiming at the manipulation of crystallization, namely, fast and slow cooling, isothermal melt- and cold-crystallization. Subsequently, we evaluated the changes recorded in the overall thermal behavior, semicrystalline morphology and molecular mobility (segmental and local). The molecular dynamics map for neat PPAd is presented here for the first time. Unexpectedly, the glass transition temperature, Tg, in the amorphous state drops upon crystallization by 8–50 K. The drop becomes stronger with the increase in the PPAd fraction. Compared to the amorphous state, crystallization leads to significantly faster segmental dynamics with severely suppressed cooperativity. For the PLA/PPAd copolymers, the effects are systematically stronger in the cold- as compared to the melt-crystallization, whereas the opposite happens for neat PLA. The local βPLA relaxation of PLA was, interestingly, recorded to almost vanish upon crystallization. This suggests that the corresponding molecular groups (carbonyl) are strongly involved and immobilized within the semicrystalline regions. The overall results suggest the involvement of either spatial nanoconfinement imposed on the mobile chains within the inter-crystal amorphous areas and/or a crystallization-driven effect of nanophase separation. The latter phase separation seems to be at the origins of the significant discrepancy recorded between the calorimetric and dielectric recordings on Tg in the copolymers. Once again, compared to more conventional techniques such as calorimetry, dielectric spectroscopy was proved a powerful and quite sensitive tool in recording such effects as well as in providing indirect indications for the polymer chains’ topology.

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Section: Resultssupporting

confidence: 90%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Revisiting Non-Conventional Crystallinity-Induced Effects on Molecular Mobility in Sustainable Diblock Copolymers of Poly(propylene adipate) and Polylactide

et al. 2022

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The Effect of Drying of Glycerol-Plasticized Starch upon Its Dielectric Relaxation Dynamics and Charge Transport

et al. 2023

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Properties of PLA-co-PBSu Copolymers Rapidly Synthesized by Reactive Processing

et al. 2023

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This work describes the synthesis of poly(lactic acid) by the ring-opening polymerization of L-lactide in the presence of oligo(butylene succinate) with two different molecular weights (Mn = 6100 and 16300 g/mol) as a macroinitiator during reactive processing. The macroinitiators were added in concentrations 1 wt%, 2.5 wt%, 5 wt%, 10 wt% and 15 wt% in respect to the L-lactide mass in the premix. The properties of the received copolymers were extensively studied with spectroscopic techniques, GPC, DSC, XRD, TGA as well as nanoindentation. Blocky copolymers were received with number average molecular weights ranging from 30 to 100 kg/mol, which decreased with increasing the PBSu content in the feed. The introduction of the flexible PBSu chains decreased the single glass transition detected, while DSC and XRD gave indications that both components crystallized in the copolymers with PBSu premix content > 5 wt%. Thermal stability was maintained and depended on the composition and molecular weight. Nanoindentation showed that despite the decreasing trend of hardness and elastic modulus with increasing PBSu content, the PLA-PBSu 2.5% copolymers had simultaneously higher elasticity modulus and strength compared to the other compositions, possibly because of a complementary effect of their high molecular weight and crystallinity. These copolymers were promising for production with continuous reactive extrusion, a novel, fast and economically viable method to commercially produce PLA-based polymers.

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Direct and indirect effects on molecular mobility in renewable polylactide–poly(propylene adipate) block copolymers as studied via dielectric spectroscopy and calorimetry

Abstract: In this work, we study a series of sustainable block copolymers based on polylactide, PLA, and poly(propylene adipate), PPAd, both polymers being prepared from renewable resources. Envisaging wide range of...

Cited by 13 publications

References 87 publications

Revisiting Non-Conventional Crystallinity-Induced Effects on Molecular Mobility in Sustainable Diblock Copolymers of Poly(propylene adipate) and Polylactide

Revisiting Non-Conventional Crystallinity-Induced Effects on Molecular Mobility in Sustainable Diblock Copolymers of Poly(propylene adipate) and Polylactide

The Effect of Drying of Glycerol-Plasticized Starch upon Its Dielectric Relaxation Dynamics and Charge Transport

Properties of PLA-co-PBSu Copolymers Rapidly Synthesized by Reactive Processing

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