Structural evolution of poly(l-lactide) block upon heating of the glassy ABA triblock copolymers containing poly(l-lactide) A blocks

Nagarajan, Selvaraj; Krishnan, Deepthi; Gowd, E. Bhoje

doi:10.1016/j.polymer.2016.06.031

Cited by 22 publications

(14 citation statements)

References 58 publications

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“…In general, both the T g and the T m values are observed to decrease with the increasing number of blocks in the polymer. This depression of the T g and T m values is a known phenomenon in poly( l -lactide) chemistry; 60 the inclusion of amorphous polymer segments influences the crystallization behavior of the semicrystalline PLA fragments and improves the polymer chain mobility. 61 – 63 …”

Section: Resultsmentioning

confidence: 99%

Preparation of multiblock copolymers via step-wise addition of l-lactide and trimethylene carbonate

et al. 2018

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Section: Resultsmentioning

confidence: 99%

Preparation of multiblock copolymers via step-wise addition of l-lactide and trimethylene carbonate

et al. 2018

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“…Recently, it was reported that the α form is formed through an intermediate form, i.e., mesophase or α′ form, upon the crystallization of PLLA from both melt state and glassy state. − Wasanasuk and Tashiro reported that the mesophase was transformed to the α′ form in the temperature region from T g to 120 °C, whereas it transformed to the α form in the higher temperature region above 120 °C . On the other hand, the strain-induced mesophase was induced by drawing from the amorphous phase in the temperature region of 40–70 °C. , It was also showed that the upper stability of the mesophase is 70 °C, and at around this temperature the mesophase transformed to the α′ or α forms via melting and recrystallization in drawn samples. ,, Although extensive studies have been carried out to understand the crystallization process of PLLA, the precise control of its crystallization during processing, slow crystallization rate, and poor mechanical properties of PLLA limited its practical applications.…”

Section: Introductionmentioning

confidence: 99%

Influence of Boron Nitride Nanosheets on the Crystallization and Polymorphism of Poly(l-lactide)

et al. 2018

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This work reports on the impact of delaminated boron nitride nanosheets (BNNSs) on the crystallization behavior and crystalline structure of melt-crystallized poly-L-lactic acid (PLLA). Wide-angle X-ray diffraction and scanning electron microscopy data revealed that the addition of lower loadings of BNNSs (∼0.5 wt %) resulted in the highly dispersed PLLA nanocomposites, whereas the higher loading of BNNSs (≥1 wt %) leads to the agglomerated nanocomposites. It is shown that the presence of lower loadings of the BNNSs (∼0.5 wt %) induces the formation of ordered α form when crystallizing from the melt at a cooling rate of 10 °C/min, but the mixture of α' and α forms is formed in the presence of higher loading of BNNSs (≥1 wt %). Polarized optical microscopy images revealed that the crystallization rate of PLLA was significantly enhanced in the presence of lower loading of BNNSs (∼0.5 wt %) as corroborated by the increasing number of tiny spherulites. The strong interaction between the highly dispersed BNNSs and PLLA chains induces the conformationally ordered α form, and the various experimental techniques revealed that crystallization of PLLA occurred rapidly with the narrow distribution of crystal size and degree of crystal perfection in highly dispersed nanocomposites. Furthermore, the thermal conductivity of PLLA/BNNSs nanocomposites was found to increase significantly with BNNSs loading.

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“…DSC analysis (Figures S60–S64) shows glass transition temperatures ( T g ) of 58 °C, 50 °C, and 54 °C for the LA/CHO diblock, triblock, and tetrablock copolymers, respectively, and melting temperatures of ∼154 °C. The T g value lies on the lower end for lactide-containing polymers, which is a known phenomenon in block copolymers containing lactide . The pCHO- b -PHB copolymer showed a T g of 6 °C, presumably corresponding to the PHB block, and a melting temperature of 82 °C.…”

Section: Results and Discussionmentioning

confidence: 86%

ABC and ABAB Block Copolymers by Electrochemically Controlled Ring-Opening Polymerization

et al. 2021

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An electrochemically controlled synthesis of multiblock copolymers by alternating the redox states of (salfan)Zr-(O t Bu) 2 (salfan = 1,1′-di(2-tert-butyl-6-N-methylmethylenephenoxy)ferrocene) is reported. Aided by electrochemistry with a glassy carbon working electrode, an in situ potential switch alters the catalyst's oxidation state and its subsequent monomer (Llactide, β-butyrolactone, or cyclohexene oxide) selectivity in one pot. Various multiblock copolymers were prepared, including an ABAB tetrablock copolymer, poly(cyclohexene oxide-b-lactide-bcyclohexene oxide-b-lactide), and an ABC triblock copolymer, poly(hydroxybutyrate-b-cyclohexene oxide-b-lactide). The polymers produced using this technique are similar to those produced via a chemical redox reagent method, displaying moderately narrow dispersities (1.1−1.5) and molecular weights ranging from 7 to 26 kDa.

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Structural evolution of poly(l-lactide) block upon heating of the glassy ABA triblock copolymers containing poly(l-lactide) A blocks

Cited by 22 publications

References 58 publications

Preparation of multiblock copolymers via step-wise addition of l-lactide and trimethylene carbonate

Preparation of multiblock copolymers via step-wise addition of l-lactide and trimethylene carbonate

Influence of Boron Nitride Nanosheets on the Crystallization and Polymorphism of Poly(l-lactide)

ABC and ABAB Block Copolymers by Electrochemically Controlled Ring-Opening Polymerization

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