Polymer dynamics in nanoconfinement: Interfaces and interphases

Krutyeva, Margarita; Wischnewski, A.; Richter, D.

doi:10.1051/epjconf/20158302009

Cited by 18 publications

(19 citation statements)

References 30 publications

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“…Besides the clearly geometrical constraints imposed by the nanofillers, the polymer dimension also dictates the degree of confinement, which in turn defines the enhancement or not of physical properties. Hence, 2 R < d defines a weak confinement whereas 2R ≫ d defines a strongly confined system, where R is the polymer dimension (radius of gyration or hydrodynamic radius) and d the pore diameter or gallery spacing …”

Section: Introductionmentioning

confidence: 99%

“…Hence, 2R < d defines a weak confinement whereas 2R ≫ d defines a strongly confined system, where R is the polymer dimension (radius of gyration or hydrodynamic radius) and d the pore diameter or gallery spacing. 14 In an effort to explain the behavior of at least T g in glassy polymer nanocomposites, model systems mimicking nanocomposite environments based on ultrathin films kept between parallel silica sheets (or only one surface of the polymer film in contact with the substrate) were investigated. [15][16][17][18] Nanostructured films obtained from grafted nanoparticles (gold or SiO 2 ) dispersed in a polymer in solution have also been studied to understand the influence of nanoparticlematrix interactions on the thermal properties (note that tuning the length of the grafted chains promoted or not interactions with the polymer matrix).…”

Section: Introductionmentioning

confidence: 99%

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Polymers in 2D confinement: A nanoscale mechanism for thermo‐mechanical reinforcement

Romo-Uribe

2017

Polymers for Advanced Techs

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Acrylate-clay nanocomposites, a 2D confined system, exhibited unusual increase of thermo-mechanical properties. The nature of this reinforcement can be ascribed to chain dynamics modification and therefore investigated via dynamic mechanical analysis. Transmission electron microscopy and dynamic light scattering showed a strong nanoconfined regime, 2R h ≫ d 001 , where R h is the polymer's hydrodynamic radius and d 001 is the clay gallery spacing.The geometrical constraints to polymer dynamics led to significant enhancement of the thermo-mechanical properties. Adding only 1 wt% nanoclay, the glass transition temperature increased significantly, ΔT g = T g − T g,bulk~1 0°C, and the dynamic modulus E′ increased 10-fold.Analysis of dynamic mechanical spectra showed an increase of relaxation time τ, ie, polymer dynamics retardation. Furthermore, the mechanical damping tan δ was strongly attenuated evidencing the reduction of viscous dissipation. The activation energy E a of the α-transition increased as the confined macromolecules needed to overcome higher energy barriers to achieve configurational rearrangements. The considerable increase of mechanical modulus cannot be explained by polymer composite models, rather it was associated to a "nano-effect," scaling with the degree of confinement as E/E matrix~( 2R h /d 001 )n . This study paves the road for further understanding of polymer dynamics under 2D confinement and the reinforcement mechanism of thermo-mechanical properties. 1-3 Hybrid nanoparticles are also successful to produce nanocomposites with more robust physical properties and are also being used to produce smart, shape memory polymeric networks with tailored thermo-mechanical properties. 4,5The addition of nanoclays, ie, layered silicates, to glassy and semicrystalline polymers has produced nanocomposites with enhanced mechanical, thermal, and barrier properties. For recent reviews, see Paul and Robeson 3 and Ray and Okamoto. 6 It is noted however that polymers (glassy and semicrystalline) with nanoclay concentrations in excess of 10 wt% led to relatively modest enhancement of mechanical properties, and the degree of property enhancement varies broadly according to the type of nanoclay used and the surface treatment. Furthermore, the concentration of nanoclays used also varies greatly and higher concentrations (>10%) appear contrary to the assumption that rather small concentrations of nanofiller would enhance the physical properties. 2,3It is believed that the macromolecular nanoconfinement found in, for instance, intercalated morphologies of layered silicate nanocomposites would be responsible to a larger extent for the changes of thermomechanical properties. For instance, confinement has induced lowering or increasing of the glass transition temperature, T g , in glassy polymer nanocomposites. The reduction of T g in confined small molecule glassy materials was first documented by McKenna et al. 7 The confinement in polymer nanocomposites is understood as (1) polymer chains constrained to layere...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Polymers in 2D confinement: A nanoscale mechanism for thermo‐mechanical reinforcement

Romo-Uribe

2017

Polymers for Advanced Techs

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“…The topic of bulk vs. confined organic materials is usually studied by a variety of classic experimental techniques. Changes in dynamics of various organic media as reflected by specific intrinsic probes of material, such as dynamic density fluctuations, reorientations of magnetic and electric dipoles are detected by means of neutron scattering (NS), nuclear magnetic resonance (NMR) or dielectric relaxation spectroscopy (BDS), respectively, are often observed (see general and special reviews [1][2][3][4][5][6][7][8][9]). These are related to phase transitions and eventually, to a formation of new phase(s) induced in confined organic medium (filler) by spatial restriction or/and by wall surface of confining inorganic matrix (confiner) [1][2][3][4] with their complex impacts into dynamic properties [5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Dynamics of Confined Short-Chain alkanol in MCM-41 by Dielectric Spectroscopy: Effects of matrix and system Treatments and Filling Factor

et al. 2020

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The dynamics of n-propanol confined in regular MCM-41 matrix with the pore size D pore = 40 Å, under various matrix conditioning and sample confining conditions, using broadband dielectric spectroscopy (BDS), is reported. First, various drying procedures with the capacitor filling under air or N 2 influence the BDS spectra of the empty MCM-41 and the confined n-PrOH/MCM-41 systems, but have a little effect on the maximum relaxation time of the main process. Finally, various filling factors of n-PrOH medium in the optimally treated MCM-41 system lead to unimodal or bimodal spectra interpreted in terms of the two distinct dynamic phases in the confined states.Polymers 2020, 12, 610 2 of 17 atmosphere, as well as degree of filling the pores (filling factor), of the previous specifically treated matrix with a given medium. One of the most often used model inorganic matrices based on silica such as irregular mesoporous silica gels (SG) and regular periodic mesoporous silicas (PMS), e.g., and 14], has the hydrophilic character due to the presence of three basic kinds of polar silanol groups: isolated (free) silanol [O≡Si-OH], geminal silanol or silanediol [O=Si=(OH) 2 ] and vicinal silanol [O≡Si-OH...HO-Si≡O], with their different adsorption ability to the environmental moisture (H 2 O from air) or other agents [15][16][17][18] and the capability of having various modification treatments [17,18]. Consequently, many BDS works addressed this important water-adsorption phenomenon in various silicas [19][20][21][22]. However, in spite of the importance of these external parameters, a relatively small amount of attention was devoted to systematic studies of their variations from the viewpoint of their impact into the dynamic response of the various confined organics [23,24]. This is also evident from the frequent absence of detailed descriptions of the empty matrix and confined system conditioning, as well as of the filling conditions during the preparation of the confined systems.The knowledge situation is further complicated for the special group of H-bonded compounds, a very important class of organic media. Although the simpler poly alcohols, such as 1,2-ethanediol, ethylene glycol (EG), 1,2-propanediol, propylene glycol (PG) and 1,2,3-propanetriol, glycerol (GL) were among the first model organic media investigated after insertion into various inorganic silica matrices by BDS [25][26][27][28][29][30], BDS works on confined monohydroxy alcohols are rather limited [24,[31][32][33]. This family of alcohols exhibits basically two peak features, where the main peak consists of two strongly superimposed subpeaks from the dominating Debye relaxation and the essentially less intense primary α one together with the well-separated secondary β process [34]. First, branched longer monohydroxy alkanols were studied where well-separated Debye-and α-processes were observed [31,32]. Later the first simplest members of the n-alkanol family, i.e., methanol and ethanol, were measured under confinement in MCM-41, showing a single global ...

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“…The polymer dimension also dictates the degree of confinement which in turn define the enhancement or not of physical properties. Hence, 2 R < d defines a weak confinement whereas 2 R ≫ d defines a strongly confined system; R is the polymer dimension (radius of gyration or hydrodynamic radius) and d the pore diameter or gallery spacing …”

Section: Introductionmentioning

confidence: 99%

“…Hence, 2R < d defines a weak confinement whereas 2R  d defines a strongly confined system; R is the polymer dimension (radius of gyration or hydrodynamic radius) and d the pore diameter or gallery spacing. [34][35][36] In an effort to explain the behavior of, at least T g , in glassy polymer nanocomposites, model systems mimicking confined environments based on ultrathin films were investigated. [37][38][39] Model nanostructured films have also been studied to address nanoparticle-matrix interactions and their influence on thermal properties.…”

Section: Introductionmentioning

confidence: 99%

Viscoelasticity and Dynamics of Confined Polyelectrolyte/Layered Silicate Nanocomposites: The Influence of Intercalation and Exfoliation

Romo-Uribe

Cardoso

2017

Macro Chemistry & Physics

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The influence of different confinement regimes on the linear viscoelastic properties of a polyelectrolyte, the protonated poly‐[(dimethylamino) ethyl methacrylate] (PDMAEMAH), is investigated. PDMAEMAH is reinforced with the layered silicate montmorillonite (MMT). Neat MMT and MMT treated with sulfobetaine and ammonia‐based surfactants (MMT/SB and MMT/NH, respectively) are utilized. Transmission electron microscopy and X‐ray scattering show that MMT and MMT/NH produce intercalated morphology, whereas MMT/SB produces an exfoliated morphology. Thus, the polyelectrolyte is under different confinement regimes. The confinement produces the increase of glass transition temperature Tg; however, the increase is larger for the (highly confined) intercalated morphology. Master curves are constructed applying time–temperature superposition. Strikingly, the viscoelastic spectra evidence that the intercalated morphology produces twofold increase of rubber‐like modulus, whereas the exfoliated morphology produces over fourfold reduction of rubber‐like modulus, both at 3 wt% clay concentration. The reduction of rubber‐like modulus suggests that an exfoliated morphology produces disruption of the entanglement density. Analysis in the segmental relaxation regime shows that the intercalated morphology induces longer relaxation times, that is, more dynamics retardation, in correlation with the increase of glass transition temperature. This research paves the road for better understanding of viscoelastic behavior and dynamics of molten polyelectrolytes under confinement.

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Polymer dynamics in nanoconfinement: Interfaces and interphases

Cited by 18 publications

References 30 publications

Polymers in 2D confinement: A nanoscale mechanism for thermo‐mechanical reinforcement

Polymers in 2D confinement: A nanoscale mechanism for thermo‐mechanical reinforcement

Dynamics of Confined Short-Chain alkanol in MCM-41 by Dielectric Spectroscopy: Effects of matrix and system Treatments and Filling Factor

Viscoelasticity and Dynamics of Confined Polyelectrolyte/Layered Silicate Nanocomposites: The Influence of Intercalation and Exfoliation

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