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1.
Int J Pharm ; 610: 121235, 2021 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-34743960

RESUMO

Coamorphous drug delivery systems have emerged as a promising formulation technique for improving the solubility and oral bioavailability of poorly soluble drugs. The selection of a suitable coformer is the key to obtaining a successful coamorphous formulation. This study aims to investigate the impacts of coformers with similar chemical structures but different physical properties on the crystallization behavior and molecular dynamics of binary amorphous systems. The addition of three profen analogs, ibuprofen (IBU), ketoprofen (KETO) and indoprofen (INDO) leads to significantly different effects on the crystallization kinetics of amorphous nimesulide (NIME). The crystal growth rates for amorphous NIME are substantially accelerated in the presence of IBU, but drastically reduced in the presence of INDO, while the incorporation of KETO results in a negligible effect. Broadband dielectric spectroscopy is employed to characterize the molecular dynamics of neat amorphous NIME and coamorphous systems. The addition of three structural analogs alters the molecular mobility of amorphous NIME in different ways, which is consistent with the trend observed for their impacts on the crystallization kinetics, suggesting that the relative mobility between the components of coamorphous mixtures governs the physical stability. In addition, it is found that the temperature dependence of the α-relaxation times for NIME with and without coformers is superimposed once the temperature is scaled by Tg/T, whereas the crystallization kinetics do not overlap on a Tg/T scale. This deviation can result from a complex interplay of thermodynamic and kinetic factors involved in multicomponent amorphous systems. This study provides insights into the crystallization kinetics and molecular dynamics of coamorphous systems containing drug analogs, which can potentially offer more flexibility for the control of physical stability without sacrificing therapeutic efficacy.

2.
Adv Mater ; : e2104747, 2021 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-34558121

RESUMO

In order to apply polymer semiconductors to stretchable electronics, they need to be easily deformed under strain without being damaged. A small number of conjugated polymers, typically with semicrystalline packing structures, have been reported to exhibit mechanical stretchability. Herein, a method is reported to modify polymer semiconductor packing-structure using a molecular additive, dioctyl phthalate (DOP), which is found to act as a molecular spacer, to be inserted between the amorphous chain networks and disrupt the crystalline packing. As a result, large-crystal growth is suppressed while short-range aggregations of conjugated polymers are promoted, which leads to an improved mechanical stretchability without affecting charge-carrier transport. Due to the reduced conjugated polymer intermolecular interactions, strain-induced chain alignment and crystallization are observed. By adding DOP to a well-known conjugated polymer, poly[2,5-bis(4-decyltetradecyl)pyrrolo[3,4-c]pyrrole-1,4-(2H,5H)-dione-(E)-1,2-di(2,2'-bithiophen-5-yl)ethene] (DPPTVT), stretchable transistors are obtained with anisotropic charge-carrier mobilities under strain, and stable current output under strain up to 100%.

3.
J Colloid Interface Sci ; 595: 151-158, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33819690

RESUMO

Recently, two-dimensional transition metal carbide/nitride (MXene) and its composites with polymers have attracted great interest from researchers due to their potential applications in flexible electronics, electromagnetic shielding, catalysis, and energy storage. However, the easy oxidation of MXene and the low efficiency of traditional composites preparation methods have brought great challenges to the practical application of polymer/MXene composites. Here, we prepared polystyrene/Mxene (PS/MXene) composites with a 3D conductive network structure through particle construction strategy. Because of the compact and ordered structure, the conductivity of the material reached 3846.15 S/m when the filler content was only 1.81 vol%, and it can retain 53.4% of the initial value after 180 days. Furthermore, based on the 3D network, we orientated the MXene nanosheets in the matrix to form the MXene orientated 3D network binary structure. This unique structure design further increased the utilization rate of MXene and made the material conductivity reach to 4471.13 S/m, with the percolation threshold as low as 0.175 vol%. We believe that this research can provide a feasible way for the practical application of MXene composite materials.

4.
ChemSusChem ; 13(13): 3447-3454, 2020 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-32368825

RESUMO

Aluminum-ion batteries (AIBs) are regarded as one of the most promising types of energy storage device in light of the safety, natural abundance, and electrochemical properties of aluminum. However, the rate capabilities of AIBs are limited owing to the sluggish kinetics of chloroaluminate anions. In this study, a covalent organic framework (COF) is adopted as the cathode material in AIBs. Theoretical and experimental results suggest that the COFs allow fast anion diffusion and intercalation without structure collapse, owing to the robust frameworks and the hierarchical pores with a large specific surface area of 1794 m2 g-1 . The resultant AIB exhibits remarkable long-term stability, with a reversible discharge capacity of 150 mAh g-1 after 13 000 cycles at 2 A g-1 . It also shows an excellent rate capability of 113 mAh g-1 at 5 A g-1 . This work fully demonstrates the potential of COFs in the storage of chloroaluminate anions and other large-sized ions.

5.
Soft Matter ; 16(2): 375-382, 2020 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-31803877

RESUMO

The self-assembly of triphenylene (TP)-based side-chain discotic liquid crystalline polymers (SDLCPs) with different grafting densities was investigated by using the dissipative particle dynamics (DPD) method. We explored the coupling effect between the main chain and the side-chain TP discogens with various length alkyl tails, and how the rigidity of the main chain, grafting density and spacer lengths affect the self-assembled morphologies of SDLCPs. By changing the above factors, we have obtained nine phases. It is deduced that a moderate grafting density, a polymer backbone with sufficient length and alkyl tails with medium length ensure SDLCPs form ordered columnar mesophases. It is worth noting that double columnar phases (Colne-Col and Colh-Col) were obtained with high grafting densities and sufficiently long backbones. All these results provide an effective basis and helpful guidance for the in-depth research of such kinds of fascinating organic semiconducting materials, SDLCPs, from the perspective of grafting density.

6.
Nat Mater ; 18(6): 594-601, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30988452

RESUMO

Stretchable semiconducting polymers have been developed as a key component to enable skin-like wearable electronics, but their electrical performance must be improved to enable more advanced functionalities. Here, we report a solution processing approach that can achieve multi-scale ordering and alignment of conjugated polymers in stretchable semiconductors to substantially improve their charge carrier mobility. Using solution shearing with a patterned microtrench coating blade, macroscale alignment of conjugated-polymer nanostructures was achieved along the charge transport direction. In conjunction, the nanoscale spatial confinement aligns chain conformation and promotes short-range π-π ordering, substantially reducing the energetic barrier for charge carrier transport. As a result, the mobilities of stretchable conjugated-polymer films have been enhanced up to threefold and maintained under a strain up to 100%. This method may also serve as the basis for large-area manufacturing of stretchable semiconducting films, as demonstrated by the roll-to-roll coating of metre-scale films.

7.
Macromol Rapid Commun ; 39(14): e1800092, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29749111

RESUMO

The understanding of the structure-mechanical property relationship for semiconducting polymers is essential for the application of flexible organic electronics. Herein pseudo free-standing tensile testing, a technique that measures the mechanical property of thin films floating on the surface of water, is used to obtain the stress-strain behaviors of two semiconducting polymers, poly(3-hexylthiophene) (P3HT) and poly(2,5-bis(2-decyltetradecyl)-3,6-di(thiophen-2-yl)diketopyrrolo[3,4-c]pyrrole-1,4-dione-alt-thienovinylthiophene (DPP-TVT) donor-acceptor (D-A) polymer. To our surprise, DPP-TVT shows similar viscoelastic behavior to P3HT, despite DPP-TVT possessing a larger conjugated backbone and much higher charge carrier mobility. The viscoelastic behavior of these polymers is due to sub room temperature glass transition temperatures (Tg ), as shown by AC chip calorimetry. These results provide a comprehensive understanding of the viscoelastic properties of conjugated D-A polymers by thickness-dependent, strain rate dependent, hysteresis tests, and stress-relaxation tests, highlighting the importance of Tg for designing intrinsically stretchable conjugated polymers.


Assuntos
Polímeros/química , Pirazóis/química , Pirimidinas/química , Tiofenos/química , Vidro/química , Semicondutores , Resistência à Tração , Temperatura de Transição
8.
Polymers (Basel) ; 10(9)2018 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-30960932

RESUMO

The critical overlap concentration C* is an important concept in polymer solutions and is defined as the boundary between dilute and semidilute regimes. In this study, the chain conformational changes of polystyrene (PS) with both high (Mn = 200,000 Da) and low (Mn = 13,000 Da) molecular weights in cis-decalin were compared by intrachain fluorescence resonance energy transfer (FRET). The random labeling of donor and acceptor chromophores strategy was employed for long PS chains, whereas chain-end labeling was used for short PS chains. By monitoring the spectroscopic intensity ratio between acceptor and donor, the concentration dependence on chain conformation from dilute to semidilute solutions was determined. Both long and short chains exhibit a conformational transition concentration, above which the polymer chains begin to collapse with concentration significantly. Interestingly, for randomly labeled polymer long chains, such concentration is consistent with C* determined from the viscosity result, below which only slight conformational change of polymer chain takes place. However, for the chain-end labeled short chain, the conformational transition concentration takes place earlier than C*, below which no significant polymer conformation change is observed.

9.
Mol Pharm ; 14(12): 4694-4704, 2017 12 04.
Artigo em Inglês | MEDLINE | ID: mdl-29125764

RESUMO

Physical stability of pharmaceutical amorphous solid dispersions is one of the critical attributes to the successful development of the formulation. Herein, we studied the impact of low-concentration poly(ethylene oxide) (PEO) on the crystallization rates of three polymorphs of indomethacin (IMC, γ-, α-, and δ-form). We observed that the addition of 3% w/w PEO significantly increased the crystal growth rates of γ-form and α-form of IMC, but had a negligible effect on the δ-form. The reduction of the activation energy for the crystal growth of IMC polymorphs after adding the PEO follows the order γ-form > α-form > δ-form, which is consistent with the trend toward the accelerating effects of PEO on the crystal growth rates of three polymorphs. With the addition of low-concentration PEO, there is an increase of molecular mobility of IMC as evidenced by the decreased structural relaxation times and viscosities. This study suggests that the substantially different effects of PEO on the crystal growth rates of IMC polymorphs are attributable to the different adsorption of PEO on the crystal surface of those polymorphs, which in turn exerts a selective accelerating effect on IMC molecules to organize into the different crystalline phases. These findings are relevant for understanding the crystallization behavior of amorphous solid dispersions containing polymorphic drugs.


Assuntos
Cristalização/métodos , Indometacina/química , Polietilenoglicóis/química , Varredura Diferencial de Calorimetria , Química Farmacêutica , Espectroscopia Dielétrica , Composição de Medicamentos , Estabilidade de Medicamentos , Microscopia Óptica não Linear , Solubilidade , Espectroscopia de Infravermelho com Transformada de Fourier , Viscosidade
10.
J Phys Chem B ; 121(47): 10704-10716, 2017 11 30.
Artigo em Inglês | MEDLINE | ID: mdl-29111765

RESUMO

The production and stabilization of amorphous drugs by the nanoconfinement effect has recently become a research hotspot in pharmaceutical sciences. Herein, two guest/host systems, indomethacin (IMC) and griseofulvin (GSF) confined in anodic aluminum oxide (AAO) templates with different pore diameters (25-250 nm) are investigated by differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (BDS). The crystallization of the confined drugs is suppressed, and their glass transition temperatures show an evident pore-size dependency. Moreover, a combination of dielectric and calorimetric results demonstrates that the significant change in the temperature dependence of the structural relaxation time during the cooling process is attributed to the vitrification of the interfacial molecules and the local density heterogeneity under isochoric confinement. Interestingly, compared with the case of IMC/AAO, which can be described by a typical two-layer model, GSF/AAO presents an rare scenario of three glass transition temperatures under fast cooling (40-10 K/min), indicating that there exists a thermodynamic nonequilibrium interlayer between the bulk-like core and interfacial layer. In contrast, the slow cooling process (0.5 K/min) would lead confined GSF into the stable core-shell nanostructure. Using surface modification, the interfacial effect is confirmed to be an important reason for the different phenomena between these two guest/host systems, and intermolecular hydrogen bonding is also suggested to be emphasized considering the long-range effect of interfacial interactions. Our results not only provide insight into the glass transition behavior of geometrically confined supercooled liquids, but also offer a means of adjusting and stabilizing the nanostructure of amorphous drugs under two-dimensional confinement.


Assuntos
Óxido de Alumínio/química , Griseofulvina/química , Indometacina/química , Simulação de Dinâmica Molecular , Nanoestruturas/química , Varredura Diferencial de Calorimetria , Ligação de Hidrogênio , Termodinâmica
11.
Mol Pharm ; 14(7): 2262-2272, 2017 07 03.
Artigo em Inglês | MEDLINE | ID: mdl-28548840

RESUMO

This study aims to investigate the crystallization behavior and molecular dynamics of amorphous griseofulvin (GSF) in the presence of low-concentration poly(ethylene oxide) (PEO). We observe that the addition of 3% w/w PEO remarkably increases the crystal growth rate of GSF by two orders of magnitude in both the supercooled liquid and glassy states. The liquid dynamics of amorphous GSF in the presence and absence of PEO are characterized by dielectric spectroscopy. With an increase of the PEO content, the α-relaxation times of the systems decrease, indicating the increase of global molecular mobility. The couplings between molecular mobility and crystallization kinetics of GSF systems show strong time-dependences below Tg. The overlapping of α-relaxation times of GSF in presence and absence of PEO as a function of Tg/T suggest the "plasticization" effect of PEO additives. However, the crystallization kinetics of amorphous GSF containing low-concentration PEO do not overlap with those of pure GSF on a Tg/T scale. The remarkable accelerating effect of crystal growth of amorphous GSF by low-concentration PEO can be partially attributed to the increase of global mobility. The high segmental mobility of PEO is expected to strongly affect the crystal growth rates of GSF. These findings are relevant for understanding and predicting the physical stability of amorphous pharmaceutical solid dispersions.


Assuntos
Griseofulvina/química , Polietilenoglicóis/química , Varredura Diferencial de Calorimetria , Cristalização , Espectroscopia Dielétrica , Cinética , Simulação de Dinâmica Molecular , Temperatura
12.
Science ; 355(6320): 59-64, 2017 01 06.
Artigo em Inglês | MEDLINE | ID: mdl-28059762

RESUMO

Soft and conformable wearable electronics require stretchable semiconductors, but existing ones typically sacrifice charge transport mobility to achieve stretchability. We explore a concept based on the nanoconfinement of polymers to substantially improve the stretchability of polymer semiconductors, without affecting charge transport mobility. The increased polymer chain dynamics under nanoconfinement significantly reduces the modulus of the conjugated polymer and largely delays the onset of crack formation under strain. As a result, our fabricated semiconducting film can be stretched up to 100% strain without affecting mobility, retaining values comparable to that of amorphous silicon. The fully stretchable transistors exhibit high biaxial stretchability with minimal change in on current even when poked with a sharp object. We demonstrate a skinlike finger-wearable driver for a light-emitting diode.

13.
Macromol Rapid Commun ; 38(2)2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27873430

RESUMO

Novel difunctional initiators that incorporate Förster/fluorescence resonance energy transfer (FRET) pairs are generated to carry out atom transfer radical polymerization of styrene, methyl methacrylate, and n-butyl methacrylate monomers by an efficient manner. Based on the chemical structures of the initiators, the locations of the fluorophore moiety are dictated to be in the center of the chain with accurately quantified chain functionality (>90% labeling ratio). The site-specific integration of FRET dyes into separate polymer chain centers allows for characterization of the well-defined interchain distance quantitatively based on the response between these fluorescent probes. The reliability of this technique is verified in bulk state, which is in well agreement with the theoretical ones. This well-defined FRET system is expected to be a promising candidate to provide a distinct physical image at a microscopic level regarding scaling chain dimension, chain interpenetration, and polymer compatibility.


Assuntos
Corantes Fluorescentes/química , Polimerização , Polímeros/síntese química , Transferência Ressonante de Energia de Fluorescência , Radicais Livres/química , Estrutura Molecular , Polímeros/química
14.
ACS Biomater Sci Eng ; 3(12): 3133-3140, 2017 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-33445356

RESUMO

Although the role of 3,4-dihydroxyphenyl-L-alanine(DOPA)in mussel foot proteins (mfps) in the realization of underwater bonding has been widely recognized, the role of the polarity of the polymer was largely overlooked. Here, by systematically comparing the underwater bonding properties of four mussel-inspired adhesives with different amide/lactam contents but similar catechol contents and molecular weights, we came to the conclusion that the polarity of the polymers also contributes to the strong underwater bonding. With the increase in the amide/lactam contents, the polarity of the polymeric adhesive increases, which correlates to the improved underwater bonding strength. A dielectric constant is introduced to evaluate the polarity of the polymer, which may be used as a guidance for the design of mussel-inspired adhesives with even better underwater bonding properties.

15.
Artigo em Inglês | MEDLINE | ID: mdl-26465472

RESUMO

The glass transition behavior of polystyrene (PS) nanotubes confined in cylindrical alumina nanopores was studied as a function of pore diameter (d) and polymer tube thickness (δ). Both the calorimetric glass transition temperature and the microstructure measured by a nonradiative energy transfer method indicated that the polymer nanotube, or concave polymer thin film, exhibited significant differences in vitrification behavior compared to the planar one. A closer interchain proximity and an increased T_{g} were observed for polymer nanotubes with respect to the bulk polymer. T_{g} for polymer nanotubes was primarily dependent on the curvature radius d of the template, while it was less dependent on the thickness δ of the PS tube wall in the range of 11-23 nm. For small nanotubes (d=55nm), the T_{g} increased as high as 18 °C above the bulk value. This vitrified property reverted back to the bulk value when the substrate was chemically removed, which indicated the crucial importance of the interfacial effect imposed by the hard wall with a concave geometry.

16.
J Phys Chem B ; 119(15): 5047-54, 2015 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-25807007

RESUMO

The glass transitions of poly(methyl methacrylate) (PMMA) oligomer confined in alumina nanopores with diameters much larger than the polymer chain dimension were investigated. Compared with the case of 80 nm nanopores, PMMA oligomer confined in 300 nm nanopores shows three glass transition temperatures (from from low to high, denoted as Tg,lo, Tg,inter, and Tg,hi). Such phenomenon can be interpreted by a three-layer model: there exists an interphase between the adsorbed layer and core volume called the interlayer, which has an intermediate Tg. The behavior of multi-Tg parameters is ascribed to the propagation of the interfacial interaction during vitrifaction process. Besides, because of the nonequilibrium effect in the adsorbed layer, the cooling rate plays an important role in the glass transitions: the fast cooling rate generates a single Tg; the intermediate cooling rate induces three Tg values, while the ultraslow cooling rate results in two Tg values. With decreasing the cooling rate, the thickness of interlayer would continually decrease, while those of the adsorbed layer and core volume gradually increase; meanwhile, the Tg,lo gradually increases, Tg,inter almost stays constant, and the Tg,hi value keeps decreasing. In such a process, the dynamic exchanges between the interlayer and adsorbed layer, core volume should be dominant.

17.
Rev Sci Instrum ; 85(7): 074901, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-25085160

RESUMO

A stage-type ultrafast scanning calorimetry (ST-UFSC) with controlled heating and cooling rates up to 10(5) K s(-1) was designed to integrate with microstructural characterization. This enables us to precisely control the evolution of fast transitional states of metastable samples provided by the UFSC platform, and to follow subtle structural changes between intermediate stages. As an example, we collected the Raman spectra of poly(ethylene terephthalate) quenched at different crystallization states obtained by programed rapid cooling and heating processes. Because of the very small sample mass for UFSC measurements, from minimum few nanograms to sub-micrograms, the sample's temperature is very sensitive to the perturbation from the laser illumination of the Raman spectrometer. Real time temperature monitoring and compensation was accompanied during the whole process of in situ spectroscopy. The results showed a good agreement of crystallization kinetics obtained from the Raman spectroscopy and from the calorimetric melting enthalpy, given that the sample temperature is well controlled during spectroscopic measurements and that the heating rate for calorimetry is fast enough to suppress structural reorganization during heating scans. We expect that the ST-UFSC is suitable to be integrated with other micro-analysis techniques to investigate the structure and dynamics of metastable states obtained by fast thermal treatments.

18.
Nanoscale Res Lett ; 9(1): 359, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25114650

RESUMO

The morphology and the phase diagram of ABC triblock copolymer thin film directed by polymer brushes are investigated by the self-consistent field theory in three dimensions. The polymer brushes coated on the substrate can be used as a good soft template to tailor the morphology of the block copolymer thin films compared with those on the hard substrates. The polymer brush is identical with the middle block B. By continuously changing the composition of the block copolymer, the phase diagrams are constructed for three cases with the fixed film thickness and the brush density: identical interaction parameters, frustrated and non-frustrated cases. Some ordered complex morphologies are observed: parallel lamellar phase with hexagonally packed pores at surfaces (LAM3 (ll) -HFs), perpendicular lamellar phase with cylinders at the interface (LAM(⊥)-CI), and perpendicular hexagonally packed cylinders phase with rings at the interface (C2 (⊥)-RI). A desired direction (perpendicular or parallel to the coated surfaces) of lamellar phases or cylindrical phases can be obtained by varying the composition and the interactions between different blocks. The phase diagram of ABC triblock copolymer thin film wetted between the polymer brush-coated surfaces is very useful in designing the directed pattern of ABC triblock copolymer thin film.

19.
Eur Phys J E Soft Matter ; 36(4): 9851, 2013 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-23605566

RESUMO

The temperature-concentration behavior of physical gel by atactic poly(methyl methacrylate) (aPMMA) in poly(ethylene glycol) oligomer (PEG400) was investigated. A liquid-liquid demixing interferes with a glass transition during cooling. The combination of demixing and T g leads to the formation of amorphous gels at low temperature. We suggest that the gelation of aPMMA/PEG400 is a glassy gel, in which short-range attractive depletion interaction in the polymer/oligomer system was the driving force at molecular level.


Assuntos
Polietilenoglicóis/química , Polimetil Metacrilato/química , Temperatura , Géis , Reologia , Soluções , Termodinâmica
20.
J Am Chem Soc ; 125(39): 11774-5, 2003 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-14505372

RESUMO

The depletion interaction was reported to drive the mixtures of rodlike colloids and polymer coils into a variety of phase transitions such as isotropic-nematic, nematic-smectic, and so forth. We describe in this Communication a convenient preparation of the self-assembled monolayer of the platelike porphyrin molecules by the depletion interaction between the absorbent and the metal substrates. After the depletant, low molecular weight poly(ethylene oxide) (PEO), was added into the porphyrin/ethanol solution, random oriented porphyrin was then regulated to lie parallel to the adjacent metal substrates, forming the self-assembled monolayer.

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