Cyclic Structures in Polymer Model Networks

Lang, Michael

doi:10.1002/masy.201800168

Cited by 10 publications

(15 citation statements)

References 89 publications

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“…Nevertheless, it is certainly of interest to analyze the impact of statistical fluctuations in composition in case of end-linking reactions because end-linking reactions are the literature standard for gelation studies of model networks. This point is also of relevance for high conversions, as composition fluctuations freeze in during the cross-linking reaction …”

Section: Introductionmentioning

confidence: 87%

“…Recently, Nishi et al 94 report gel point conversions of a copolymerization of 4-functional stars in the inset of their Figure 3, which we have plotted also in Figure 14. This particular type of reaction suppresses loops made of an odd number of elastic strands, 46 and thus, there are no pending loops present in these networks. Nevertheless, there is still a significant delay of the gel point with respect to the ideal gel point at 1/(f − 1).…”

Section: Experimental Gel Point Datamentioning

confidence: 99%

“…This point is also of relevance for high conversions, as composition fluctuations freeze in during the cross-linking reaction. 46 The third point is explained best when comparing the average number of possible neighbors, P, to which a node can connect in typical percolation studies with GS. In bond percolation, where bonds are introduced within a range R, the number of neighbors is typically a constant number, roughly P ≈ ρR 3 , where ρ is the number density of nodes.…”

Section: ■ Introductionmentioning

confidence: 99%

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Analysis of the Gel Point of Polymer Model Networks by Computer Simulations

Lang

Müller

2020

Macromolecules

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The gel point of end-linked model networks is determined from computer simulation data. It is shown that the difference between the true gel point conversion, p c , and the ideal mean field prediction for the gel point, p c,id , is a function of the average number of cross-links per pervaded volume of a network strand, P , and thus, contains an explicit dependence on junction functionality f . On the contrary, the amount of intra-molecular reactions at the gel point is independent of f in a first approximation and exhibits a different power law dependence on the overlap number of elastic strands as compared to the gel point delay p c − p c,id . Therefore, p c − p c,id cannot be predicted from intramolecular reactions and vice versa in contrast to a long standing proposal in literature.Instead, the main contribution to p c − p c,id for P > 1 arises from the extra bonds (XB) needed to bridge the gaps between giant molecules separated in space and scales roughly ∝ (P − 1) −1/2 . Further corrections to scaling are due to non-ideal reaction kinetics, composition fluctuations, and incompletely screened excluded volume, which are discussed briefly.

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Section: Introductionmentioning

confidence: 87%

Section: Experimental Gel Point Datamentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Analysis of the Gel Point of Polymer Model Networks by Computer Simulations

Lang

Müller

2020

Macromolecules

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“…Furthermore, the computer simulations can be used to determine the gel point and its suppression, systematically identify and quantify network ”defects” (dangling ends and primary loops such as those in Figure ), and determine network topology including all higher-order loops (section ). ,− …”

Section: Prediction: Computer Simulationmentioning

confidence: 99%

Molecular Characterization of Polymer Networks

et al. 2021

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Polymer networks are complex systems consisting of molecular components. Whereas the properties of the individual components are typically well understood by most chemists, translating that chemical insight into polymer networks themselves is limited by the statistical and poorly defined nature of network structures. As a result, it is challenging, if not currently impossible, to extrapolate from the molecular behavior of components to the full range of performance and properties of the entire polymer network. Polymer networks therefore present an unrealized, important, and interdisciplinary opportunity to exert molecular-level, chemical control on material macroscopic properties. A barrier to sophisticated molecular approaches to polymer networks is that the techniques for characterizing the molecular structure of networks are often unfamiliar to many scientists. Here, we present a critical overview of the current characterization techniques available to understand the relation between the molecular properties and the resulting performance and behavior of polymer networks, in the absence of added fillers. We highlight the methods available to characterize the chemistry and molecular-level properties of individual polymer strands and junctions, the gelation process by which strands form networks, the structure of the resulting network, and the dynamics and mechanics of the final material. The purpose is not to serve as a detailed manual for conducting these measurements but rather to unify the underlying principles, point out remaining challenges, and provide a concise overview by which chemists can plan characterization strategies that suit their research objectives. Because polymer networks cannot often be sufficiently characterized with a single method, strategic combinations of multiple techniques are typically required for their molecular characterization.

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“…There are viable synthesis strategies to obtain ACNs; however, obtaining networks with defined structures either proves difficult [1] or certain criteria for model networks remain unmet [12,13]. Sakai et al [14] demonstrated a promising pathway to control polymer network structures and minimize network defects.…”

Section: Introductionmentioning

confidence: 99%

Amphiphilic Polymer Conetwork Gel Films Based on Tetra-Poly(ethylene Glycol) and Tetra-Poly(ε-Caprolactone)

et al. 2022

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The preparation and investigation of gel films from a model amphiphilic polymer conetwork (ACN) grant a deeper control and understanding of the structure–property relationship in the bulk phase and at the interface of materials with promising applications. In order to allow the simultaneous transport of hydrophilic and hydrophobic substances, polymeric networks with finely distributed hydrophilic and hydrophobic components are very suitable. When designing new soft materials such as coatings, in addition to the structure in the bulk phase, the structure at the interface plays a critical role. In this study, two alternating tetra-arm star polymers poly(ε-caprolactone) (tetra-PCL-Ox) and amino-terminated poly(ethylene glycol) (tetra-PEG-NH2) form an amphiphilic polymer conetwork. The correlation between different synthesis strategies for gel films of this ACN model system and their resulting properties will be described. Through various spin coating techniques, control over film thickness and roughness is achievable and highlights differences to macroscopic gel samples. Atomic force microscopy (AFM) measurements reveal the effect of solvents of different polarities on the swelling ability and surface structure. This correlates with AFM investigations of the mechanical properties on ACN gel films, demonstrating a strong effect on the resulting elastic modulus E, depending on the presence or absence of a good solvent during synthesis. Furthermore, a higher E modulus is obtained in the presence of the selective solvent water, compared to the non-selective solvent toluene. This observation is explained through selective swelling of the tetra-arm star polymers displaying a different hydrophobicity.

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Cyclic Structures in Polymer Model Networks

Cited by 10 publications

References 89 publications

Analysis of the Gel Point of Polymer Model Networks by Computer Simulations

Analysis of the Gel Point of Polymer Model Networks by Computer Simulations

Molecular Characterization of Polymer Networks

Amphiphilic Polymer Conetwork Gel Films Based on Tetra-Poly(ethylene Glycol) and Tetra-Poly(ε-Caprolactone)

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