Nanostructural heterogeneity in polymer networks and gels

2015 ◽  
Vol 6 (31) ◽  
pp. 5515-5528 ◽  
Author(s):  
F. Di Lorenzo ◽  
S. Seiffert
Keyword(s):  
Polymer Network ◽  
Polymer Networks ◽  
Polymer Gels ◽  
Network Heterogeneity

Many polymer gels display network defects and crosslinking inhomogeneity. This review reflects and interrelates investigations on the characterization of such polymer-network heterogeneity and on its impact on the swelling, elasticity, and permeability of polymer gels.

Direct characterization of a polymer network through its retainable units

2019 ◽  
Vol 10 (35) ◽  
pp. 4837-4843
Author(s):  
Xiaoyan Xu ◽  
Qi Wang
Keyword(s):  
Polymer Network ◽  
Polymer Networks ◽  
Quantitative Characterization

A partially decrosslinkable network provides a general protocol for full, direct and quantitative characterization of polymer networks through its retainable units.

Effect of Nematic Order Coupling on the Phase Diagrams of Side-Chain Polymer Gels with Liquid Crystal Solvent

e-Polymers ◽  
2006 ◽  
Vol 6 (1) ◽  
Author(s):  
Richard Vendamme ◽  
Ulrich Maschke
Keyword(s):  
Phase Diagram ◽  
Polymer Network ◽  
Polymer Networks ◽  
Polymer Gels ◽  
Side Chain ◽  
Miscibility Gap ◽  
Polymer Backbone ◽  
Chain Polymer ◽  
Nematic Order ◽  
Solvent Lead

AbstractWe have explored the influence of nematic order coupling on the swelling and phase diagram of polymer networks in nematogenic low molar weight LC solvent, in view of the increasing importance of such systems in advanced optical devices. Firstly, one isotropic polyacrylate network and one nematic sidechain polyacrylate network is prepared. Immersing these two networks in nematic LC solvent lead to the formation of well-defined polymer gels with LC solvents and allow us to establish the phase diagram of these relatively new materials in the concentration-temperature frame. Results were critically analysed as a function of temperature and network nature (isotropic or nematic). We demonstrate that in the case of gel made from an isotropic polymer network, the LC solvents fails to form a nematic phase inside the gel due to the lack of anisotropic coupling. Moreover, in that case the gel shrinks below TNI Solvent because of a strong “entropic” incompatibility between the isotropic flexible coils and the LC nematogens. However, the situation is drastically different in the case of LC side-chain network due to a strong coupling of the nematic order between the mesogens of the solvents and those of the polymer backbone. In that case, tremendous distortions appear in the phase-diagram, in which we especially emphasize the apparition of a stable nematic gel phase and a miscibility gap between TNI Solvent and TNI Gel. Finally, results are critically examined and compared to the few studies found in the literature.

Correlation between Mechanical Properties and Structure in Polymer Gels with Controlled Network Structure

2014 ◽  
Vol 1622 ◽  
pp. 7-16
Author(s):  
Takamasa Sakai ◽  
Yuki Akagi ◽  
Ung-il Chung
Keyword(s):  
Elastic Modulus ◽  
Fracture Energy ◽  
Molecular Design ◽  
Structural Parameters ◽  
Polymer Network ◽  
Polymer Networks ◽  
Network Models ◽  
Polymer Gels ◽  
Reaction Conversion ◽  
First Time

ABSTRACTElastmeric materials are of great importance in both academic and industrial field due to the soft and highly stretchable properties. Thus, many theories and models are proposed to correlate the physical properties and structural parameters. However, in general, it is difficult to validate these models experimentally. Thus, to this day, we do not know the requirement conditions for each model or even the validity of each model. The validation of these models has been inhibited by the inherent heterogeneity of polymer networks.Recently, we, for the first time, succeeded in fabricating polymer network with extremely suppressed heterogeneity with a novel molecular design of prepolymers. The homogeneous polymer network, called Tetra-PEG gel, is prepared by AB-type crosslink-coupling of mutually reactive tetra-arm prepolymers. In this study, we examined the models of elastic modulus and fracture energy using Tetra-PEG gel as a model system. We controlled the structural parameters with tuning the molecular weight and concentration of prepolymers, and reaction conversion of the reaction. This series of controlled network structures, for the first time, enabled us to quantitatively examine these models. We performed the stretching and tearing measurements for these polymer gels. As for the elastic modulus, we observed the shift of the models from the phantom to affine network models around the overlapping concentration of prepolymers. As for the fracture energy, we confirmed the validity of the Lake-Thomas model, which is the most popular model predicting fracture energies of elastomers.

Freeze-etch TEM of aqueous polymer gel network morphology

1986 ◽  
Vol 44 ◽  
pp. 796-797
Author(s):  
J. A. N. Zasadzinski ◽  
R. K. Prud'homme
Keyword(s):  
Metal Ion ◽  
Polymer Network ◽  
Polymer Gels ◽  
Polymer Gel ◽  
Deformation History ◽  
Crosslinked Polymer ◽  
Aqueous Polymer ◽  
History Of ◽  
Gel Network ◽  
Network Morphology

The rheological and mechanical properties of crosslinked polymer gels arise from the structure of the gel network. In turn, the structure of the gel network results from: thermodynamically determined interactions between the polymer chain segments, the interactions of the crosslinking metal ion with the polymer, and the deformation history of the network. Interpretations of mechanical and rheological measurements on polymer gels invariably begin with a conceptual model of,the microstructure of the gel network derived from polymer kinetic theory. In the present work, we use freeze-etch replication TEM to image the polymer network morphology of titanium crosslinked hydroxypropyl guars in an attempt to directly relate macroscopic phenomena with network structure.

Characterization of bi-layered magnetic nanoparticles synthesized via two-step surface-initiated ring-opening polymerization

2015 ◽  
Vol 87 (11-12) ◽  
pp. 1085-1097 ◽  
Author(s):  
Li Wang ◽  
Stefan Baudis ◽  
Karl Kratz ◽  
Andreas Lendlein
Keyword(s):  
Magnetic Nanoparticles ◽  
Ring Opening ◽  
Average Molecular Weight ◽  
Polymer Networks ◽  
Gel Permeation Chromatography ◽  
Degree Of Crystallinity ◽  
Scanning Calorimetry ◽  
H Nmr ◽  
Transmission Electron

AbstractA versatile strategy to integrate multiple functions in a polymer based material is the formation of polymer networks with defined nanostructures. Here, we present synthesis and comprehensive characterization of covalently surface functionalized magnetic nanoparticles (MNPs) comprising a bi-layer oligomeric shell, using Sn(Oct)2 as catalyst for a two-step functionalization. These hydroxy-terminated precursors for degradable magneto- and thermo-sensitive polymer networks were prepared via two subsequent surface-initiated ring-opening polymerizations (ROPs) with ω-pentadecalactone and ε-caprolactone. A two-step mass loss obtained in thermogravimetric analysis and two distinct melting transitions around 50 and 85°C observed in differential scanning calorimetry experiments, which are attributed to the melting of OPDL and OCL crystallites, confirmed a successful preparation of the modified MNPs. The oligomeric coating of the nanoparticles could be visualized by transmission electron microscopy. The investigation of degrafted oligomeric coatings by gel permeation chromatography and 1H-NMR spectroscopy showed an increase in number average molecular weight as well as the presence of signals related to both of oligo(ω-pentadecalactone) (OPDL) and oligo(ε-caprolactone) (OCL) after the second ROP. A more detailed analysis of the NMR results revealed that only a few ω-pentadecalactone repeating units are present in the degrafted oligomeric bi-layers, whereby a considerable degree of transesterification could be observed when OPDL was polymerized in the 2nd ROP step. These findings are supported by a low degree of crystallinity for OPDL in the degrafted oligomeric bi-layers obtained in wide angle X-ray scattering experiments. Based on these findings it can be concluded that Sn(Oct)2 was suitable as catalyst for the preparation of nanosized bi-layered coated MNP precursors by a two-step ROP.

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