Mechanisms determining different planar orientations in PPO films crystallized by guest sorption

Nagendra, Baku; Golla, Manohar; Gallo, Chiara; Daniel, Christophe; Rizzo, Paola; Guerra, Gaetano; Baldino, Lucia; Reverchon, Ernesto

doi:10.1016/j.polymer.2021.124242

Cited by 11 publications

(36 citation statements)

References 58 publications

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“…In particular, the centering of the hk0 arcs on the meridian and of the 001 arc on the equator, shows the presence of c ⊥ orientation. It is worth adding that the degree of orientation, as evaluated from the azimuthal scan of the 001 reflection, is f c ≈ − 0.32, and hence close to the maximum values of degree of c ⊥ orientation as achieved for PPO films 37,51,52 …”

Section: Resultssupporting

confidence: 67%

“…[37][38][39][40] In fact, co-crystallization of PPO occurring in nanoconfined film layers leads to flat-on crystalline lamellae and hence to c ⊥ orientation. 51 However, in a very recent paper we have shown the unexpected difficulty to get c ⊥ orientation in PPO films having a thickness ≤20 μm. 52 In this paper, we define guest-induced crystallization procedures, which are suitable to induce high degree of crystallinity as well as high degrees of c ⊥ orientation of the NC α form, for thin (≤20 μm) amorphous PPO films.…”

Section: Introductionmentioning

confidence: 94%

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c‐perpendicular orientation in thin nanoporous‐crystalline poly(2,6‐dimethyl‐1,4‐phenylene)oxide films

Nagendra

Daniel

Rizzo

et al. 2022

Polymers for Advanced Techs

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Nanoporous-crystalline films of poly(2,6-dimethyl-1,4-phenylene)oxide (PPO), exhibiting c-perpendicular orientation (c ⊥ ) orientation (i.e., the orientation of the crystalline chain axes being preferentially perpendicular to the film plane), show the advantage of faster guest diffusivity and higher transparency. However, by using the methods described in the literature, this perpendicular orientation cannot be achieved for low thickness films (≤20 μm). In this paper, we describe four different preparation methods, which are suitable to get high degree of crystallinity (X c >40%) as well as high degree of c ⊥ orientation (À0.5< f c <À 0.3) of CC and NC α forms, for film thickness even as low as 5 μm. All the described methods are based on reduction of guest sorption kinetics. The reported results also confirm our previous hypothesis that c ⊥ orientation is due to formation of flat-on crystalline lamellae, which in turn are due to nanoconfined co-crystallization of PPO. An anomalous temperature dependence of c ⊥ orientation for limonene-induced co-crystallization with PPO is described and rationalized.

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Section: Resultssupporting

confidence: 67%

Section: Introductionmentioning

confidence: 94%

c‐perpendicular orientation in thin nanoporous‐crystalline poly(2,6‐dimethyl‐1,4‐phenylene)oxide films

Nagendra

Daniel

Rizzo

et al. 2022

Polymers for Advanced Techs

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“…Table 1 collects in its last column the crystalline forms (α or β) of all films characterized in this study together with those already reported in the literature ( Khulbe et al, 2000 ; Daniel et al, 2011 ; Nagendra et al, 2019 ; Golla et al, 2020b ; Nagendra et al, 2021a ; Nagendra et al, 2021b ). In Table 1 , the guest molecules are ordered on the basis of their solubility parameter (second column) while the used crystallization methods are indicated in the fourth column.…”

Section: Resultsmentioning

confidence: 98%

“…In detail, Table 2 shows that all the considered guests with molecular volumes higher than 230 Å 3 and lower than 149 Å 3 lead to the α- and β-forms, respectively. As for the guest molecular volume, it is worth adding that it also has a key role in determining the orientation (with crystalline chain axis being preferentially parallel or perpendicular to the film plane) ( Rizzo et al, 2019b ) of PPO films ( Nagendra et al, 2021b ). Table 3 shows that all guests whose solubility is lower than 0.11 mmol per 100 ml of water and higher than 2 mmol per 100 ml of water lead to the α- and β-forms, respectively.…”

Section: Resultsmentioning

confidence: 99%

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Molecular Features Behind Formation of α or β Co-Crystalline and Nanoporous-Crystalline Phases of PPO

et al. 2022

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Guest molecular features determining the formation of α and β phases of poly(2-6-dimethyl-1,4-phenylene) oxide (PPO) are explored by collecting literature data and adding many new film preparations, both by solution casting and by guest sorption in amorphous films. Independently of the considered preparation method, the α-form is favored by the hydrophobic and bulky guest molecules, while the hydrophilic and small guest molecules favor the β-form. Furthermore, molecular modeling studies indicate that the β-form inducer guests establish stronger dispersive interactions with the PPO units than the α-form inducer guests. Thus, the achievement of co-crystalline (and derived nanoporous crystalline) α- and β-forms would result from differences in energy gain due to the host–guest interactions established at the local scale.

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Hydrogen Bonded Dimer of an Alcohol with the Derived Carboxylic Acid Triggering their Sorption by Nanoporous‐crystalline PPO Films

Nagendra

Cozzolino

Acocella

et al. 2023

Chemistry A European J

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Films exhibiting nanoporous‐crystalline (NC) phases of poly(2,6‐dimethyl‐1,4‐phenylene) oxide (PPO), which are highly effective to absorb apolar organic guest molecules, are also able to absorb polar molecules (like alcohols and carboxylic acids) but only from concentrated organic solutions. NC PPO films, which do not absorb alcohols and carboxylic acids from diluted aqueous solutions, exhibits a huge uptake (even above 30wt%) of benzyl alcohol (BAL) and benzoic acid (BA), if BA is obtained by spontaneous room temperature oxidation of BAL in aqueous solution. This phenomenon is rationalized by an easy uptake, mainly by the PPO intrahelical crystalline empty channels, of a BAL/BA 1/1 hydrogen‐bonded dimer. This huge uptake of BAL/BA dimer by NC PPO films, which is also fast for films exhibiting the orientation of the crystalline helices perpendicular to the film plane (c^ orientation), can be exploited for purification of water from BAL, when present in traces. High and fast sorption of a hydrogen bonded dimer and negligible sorption of the two separate compounds is possibly unprecedented for absorbent materials.

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Mechanisms determining different planar orientations in PPO films crystallized by guest sorption

Cited by 11 publications

References 58 publications

c‐perpendicular orientation in thin nanoporous‐crystalline poly(2,6‐dimethyl‐1,4‐phenylene)oxide films

c‐perpendicular orientation in thin nanoporous‐crystalline poly(2,6‐dimethyl‐1,4‐phenylene)oxide films

Molecular Features Behind Formation of α or β Co-Crystalline and Nanoporous-Crystalline Phases of PPO

Hydrogen Bonded Dimer of an Alcohol with the Derived Carboxylic Acid Triggering their Sorption by Nanoporous‐crystalline PPO Films

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