Polymer Molecular Weight Measurement

Neira‐Velázquez, María Guadalupe; Rodríguez-Hernández, María T.; Hernández‐Hernández, Ernesto; Ruiz‐Martínez, Antelmo R. Y.

doi:10.1002/9781118480793.ch17

Cited by 20 publications

(11 citation statements)

References 32 publications

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“…

According to the relation of reduced viscosity and intrinsic viscosity, which was described by Huggins, [ η ] can be calculated as intercept of a fitting curve where reduced viscosity is plotted against the polymer concentration within the solution. k 2 is called Huggins viscosity constant and is a measure of the solvent quality, i.e., if the selected solvent is a good or poor solvent for the polymer [ 66 ].

The Mark–Houwink–Sakurada equation relates the intrinsic viscosity [ η ] to the viscosity-average molecular weight

of a polymer.…”

Section: Figure A1mentioning

confidence: 99%

Influence of Hard Segment Content and Diisocyanate Structure on the Transparency and Mechanical Properties of Poly(dimethylsiloxane)-Based Urea Elastomers for Biomedical Applications

et al. 2021

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The effect of hard segment content and diisocyanate structure on the transparency and mechanical properties of soft poly(dimethylsiloxane) (PDMS)-based urea elastomers (PSUs) was investigated. A series of PSU elastomers were synthesized from an aminopropyl-terminated PDMS (M¯n: 16,300 g·mol−1), which was prepared by ring chain equilibration of the monomers octamethylcyclotetrasiloxane (D4) and 1,3-bis(3-aminopropyl)-tetramethyldisiloxane (APTMDS). The hard segments (HSs) comprised diisocyanates of different symmetry, i.e., 4,4′-methylenebis(cyclohexyl isocyanate) (H12MDI), 4,4′-methylenebis(phenyl isocyanate) (MDI), isophorone diisocyanate (IPDI), and trans-1,4-cyclohexane diisocyanate (CHDI). The HS contents of the PSU elastomers based on H12MDI and IPDI were systematically varied between 5% and 20% by increasing the ratio of the diisocyanate and the chain extender APTMDS. PSU copolymers of very low urea HS contents (1.0–1.6%) were prepared without the chain extender. All PSU elastomers and copolymers exhibited good elastomeric properties and displayed elongation at break values between 600% and 1100%. The PSUs with HS contents below 10% were transparent and became increasingly translucent at HS contents of 15% and higher. The Young’s modulus (YM) and ultimate tensile strength values of the elastomers increased linearly with increasing HS content. The YM values differed significantly among the PSU copolymers depending on the symmetry of the diisocyanate. The softest elastomer was that based on the asymmetric IPDI. The elastomers synthesized from H12MDI and MDI both exhibited an intermediate YM, while the stiffest elastomer, i.e., that comprising the symmetric CHDI, had a YM three-times higher than that prepared with IPDI. The PSUs were subjected to load–unload cycles at 100% and 300% strain to study the influence of HS morphology on 10-cycle hysteresis behavior. At 100% strain, the first-cycle hysteresis values of the IPDI- and H12MDI-based elastomers first decreased to a minimum of approximately 9–10% at an HS content of 10% and increased again to 22–28% at an HS content of 20%. A similar, though less pronounced, trend was observed at 300% strain. First-cycle hysteresis among the PSU copolymers at 100% strain was lowest in the case of CHDI and highest in the IPDI-based elastomer. However, this effect was reversed at 300% strain, with CHDI displaying the highest hysteresis in the first cycle. In vitro cytotoxicity tests performed using HaCaT cells did not show any adverse effects, revealing their potential suitability for biomedical applications.

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“…

The Mark–Houwink–Sakurada equation relates the intrinsic viscosity [ η ] to the viscosity-average molecular weight

of a polymer.…”

Section: Figure A1mentioning

confidence: 99%

Influence of Hard Segment Content and Diisocyanate Structure on the Transparency and Mechanical Properties of Poly(dimethylsiloxane)-Based Urea Elastomers for Biomedical Applications

et al. 2021

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“…These PA solutions also enabled significant sensitivity enhancement for 13 C measurement with a similar T DNP (TCE: 7.1 s; 1-CN: 10.7 s; 1,2-DCB: 6.6 s). Notably, 1-CN showed higher enhancement (ε C,PPS+sol ∼ 43) than the other solutions, which is likely attributed to the affinity of the solvent for PPS as revealed in the analysis by high-temperature gel permeation chromatography (GPC) . Utilizing 1-CN as the PA solution instead of TCE allowed us to access a spectral range around 60–100 ppm without solvent signal overlap …”

Section: Resultsmentioning

confidence: 99%

“…Notably, 1-CN showed higher enhancement (ε C,PPS+sol ∼ 43) than the other solutions, which is likely attributed to the affinity of the solvent for PPS as revealed in the analysis by high-temperature gel permeation chromatography (GPC). 47 Utilizing 1-CN as the PA solution instead of TCE allowed us to access a spectral range around 60−100 ppm without solvent signal overlap. 31 DNP-enhanced 13 C CPMAS NMR of the PPS with TEKPol/1-CN exhibited signals assignable to the end-groups of PPS after 512 scans (∼2 h) (Figure 5e).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

End-Groups of Poly(p-phenylene sulfide) Characterized by DNP NMR Spectroscopy

et al. 2022

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Characterization of the local chemical structure of high-performance engineering plastics is essential for rational polymer blending to achieve outstanding physical properties. The inherent high chemical stability, however, has hampered their detailed characterization using conventional analytical methods. Herein, we demonstrate that dynamic nuclear polarization enhanced solid-state NMR combined with a thermal treatment approach for sample preparation enables characterization of end-groups of poly(p-phenylene sulfide) (PPS). Mildly heating PPS mixed with TEKPol/1,1,2,2tetrachloroethane (TCE) solution resulted in a high sensitivity enhancement from 13 C CPMAS signals of PPS, and further optimization of the conditions using 1-chloronaphthalene (1-CN) as a solvent led to an enhancement factor (ε) as high as ∼43, while a conventional incipient wetness impregnation method with TEKPol/TCE afforded an enhancement factor of only ∼4. Mechanistic studies with electron paramagnetic resonance and scanning electron microscopy analysis demonstrated that thermal treatment at 60 °C promoted the distribution of the PA solution into a surface layer of PPS while suppressing the decomposition of TEKPol. The developed sample preparation approach enabled us to observe 13 C and even 15 N signals assignable to end-groups of PPS in a reasonable measurement time by using a natural abundance sample. According to the observed signals, which were identified by comparing with signals from low-molecular-weight model compounds, sodium carboxylate is present at the chain-end position, suggesting that the termination step of PPS production involves an S N Ar reaction of p-chlorophenyl intermediate with the secondary amine of the ring-opened N-methylpyrrolidone used as a solvent for PPS production.

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“…As is well known, the hydrodynamic behavior of macromolecular solutions in the diluted and semidiluted nonentangled or entangled regimes can be studied by analyzing the intrinsic viscosity, which provides information about the specific hydrodynamic volume of the chain under particular conditions (constant temperature and pressure and absence of shear) in the limit of infinite dilution. According to this, and accepting that this lignin-enriched fraction is a polymeric complex that even reacts with the epoxidized triglyceride molecules, the relationship between the reduced viscosity, η red , and lignin-enriched fraction concentration allows determination of this parameter from the intercept with the ordinate axis in accordance with the following equations , where η rel and η sp are the relative and specific viscosities, respectively; η sol and η ECO1 refer to the viscosities of the lignin-thickened sample and the epoxidized castor oil; and c is the polymer concentration in g/mL, which was converted from the weight fractions using the density of the blends. In this sense, Huggins expression is the most employed procedure to determine the intrinsic viscosity [η] (eq ), which usually follows a linear relationship between η red and the concentration in the diluted and semidiluted regimes.…”

Section: Resultsmentioning

confidence: 99%

Thickening Castor Oil with a Lignin-Enriched Fraction from Sugarcane Bagasse Waste via Epoxidation: A Rheological and Hydrodynamic Approach

Cortés-Triviño

Valencia

Franco

2021

ACS Sustainable Chem. Eng.

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Thickening vegetable oils to different extents is of great interest in the design and development of new bio-based lubricant formulations, as achieving a wide range of rheological properties is crucial to the successful replacement of petroleumbased traditional counterparts. With this aim, the influence of epoxidation degree, modified by altering the reaction conditions, on the viscous flow properties of epoxidized castor oil was investigated together with the incorporation of a lignin-enriched fraction from sugarcane bagasse waste to more extensively modify the rheological properties, thereby valorizing this waste fraction. Oil thickening was achieved by promoting the cross-linking between the epoxidized oil and the lignin-enriched fraction that enables the compatibilization of both components. Castor oil epoxidation was assessed by means of standard volumetric titration methods and infrared spectroscopy. In addition, a fully rheological characterization of both epoxidized and lignin-thickened castor oils was carried out. A hydrodynamic approach was also followed, aiming to provide an estimation of the Mark−Houwink−Sakurada parameters and relate the intrinsic viscosity with the average molecular weight of the resulting epoxidized castor oil/lignocellulose macromolecular compounds. The chemical interaction between castor oil and the lignocellulosic material increased as the extent of epoxidation was increased, yielding a variety of rheological responses from Newtonian liquids of increasing viscosities (from around 1 to 500 Pa•s) to viscoelastic liquids.

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Polymer Molecular Weight Measurement

Cited by 20 publications

References 32 publications

Influence of Hard Segment Content and Diisocyanate Structure on the Transparency and Mechanical Properties of Poly(dimethylsiloxane)-Based Urea Elastomers for Biomedical Applications

Influence of Hard Segment Content and Diisocyanate Structure on the Transparency and Mechanical Properties of Poly(dimethylsiloxane)-Based Urea Elastomers for Biomedical Applications

End-Groups of Poly(p-phenylene sulfide) Characterized by DNP NMR Spectroscopy

Thickening Castor Oil with a Lignin-Enriched Fraction from Sugarcane Bagasse Waste via Epoxidation: A Rheological and Hydrodynamic Approach

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