Degradation Of Polymer Solutions Research Articles

Impact of Molecular Design on Degradation Lifetimes of Degradable Imine-Based Semiconducting Polymers.

Transient electronics are a rapidly emerging field due to their potential applications in the environment and human health. Recently, a few studies have incorporated acid-labile imine bonds into polymer semiconductors to impart transience; however, understanding of the structure-degradation property relationships of these polymers is limited. In this study, we systematically design and characterize a series of fully degradable diketopyrrolopyrrole-based polymers with engineered sidechains to investigate the impact of several molecular design parameters on the degradation lifetimes of these polymers. By monitoring degradation kinetics via ultraviolet-visible spectroscopy, we reveal that polymer degradation in solution is aggregation-dependent based on the branching point and Mn, with accelerated degradation rates facilitated by decreasing aggregation. Additionally, increasing the hydrophilicity of the polymers promotes water diffusion and therefore acid hydrolysis of the imine bonds along the polymer backbone. The aggregation properties and degradation lifetimes of these polymers rely heavily on solvent, with polymers in chlorobenzene taking six times as long to degrade as in chloroform. We develop a new method for quantifying the degradation of polymers in the thin film and observe that similar factors and considerations (e.g., interchain order, crystallite size, and hydrophilicity) used for designing high-performance semiconductors impact the degradation of imine-based polymer semiconductors. We found that terpolymerization serves as an attractive approach for achieving degradable semiconductors with both good charge transport and tuned degradation properties. This study provides crucial principles for the molecular design of degradable semiconducting polymers, and we anticipate that these findings will expedite progress toward transient electronics with controlled lifetimes.

P02 Evaluation of acoustically induced physical effects based on polymer degradation in solution(Poster session)

P02 Evaluation of acoustically induced physical effects based on polymer degradation in solution(Poster session)

Degradation of polymer solutions in a turbulent flow in a cylindrical channel

Water- and oil-soluble polymers capable to reduce the turbulent flow drag were studied. The cause of a decrease in the Toms effect under various conditions was determined. Recommendations were formulated for optimum use of the polymers in pipeline transport technologies.

Study on the Influential Factors of Shear Degradation of Polymer

In order to study the regularity of shear degradation of polymer solution, the artificial core is used to simulate the flow of polymer formation[1]. The influence of mass concentration, molecular weight and shear rate on the rheological of polymer solution is studied. And the stability of the polymer solution after degradation were analyzed through method of indoor simulation experiment Research shows that Polymer solution is degraded after shearing , the viscosity reduced and it will not rebound with the passage of time. When the solution was sheared through the porous medium, degradation rate increases with the increase of shear rate. Also it can be seen, in the case of the same concentration, the degradation rate increases with the increase of relative molecular mass. In the case of the same relative molecular mass, the degradation rate increases with the increase of the mass concentration.

Chain Degradation under Low-Intensity Sonication of Polymer Solutions in the Presence of Filler: Mechanism of Ultrasonic Degradation of Flexible Chain Macromolecules

Routine dispersion of fillers in polymer solutions in a usual ultrasonic cleaning bath has been shown to lead to chain degradation. It is the filler presence, only, that has been demonstrated to provoke chain degradation under low-intensity sonication. A critical analysis of the literature concerned with the effects arising from propagation of acoustic waves in a liquid and an experimental study of ultrasonic degradation of polymers in solution were carried out. Based on these results, the mechanisms of chain degradation were discussed. Our previously proposed universal mechanism of chain degradation in inhomogeneous hydrodynamic fields has been shown to explain the basic facts repeatedly confirmed over the years of studying the ultrasonic degradation: (i) the existence of a limiting molecular weight such that macromolecules with lower molecular weights are not subject to degradation and (ii) the dependences of degradation rate on polymer molecular weight, polymer concentration, and temperature.

The Study of Ultrasonic Degradation of Superabsorbent Hydrogels

Viscometry is a valid and practical approach for monitoring the degradation of polymers in solution. In this work, at constant power and pulse, the effects of different operating parameters such as time of irradiation, temperature, solution concentration, volume, solvent, and immersion depth of horn on the rate of degradation have been investigated in aqueous solution using laboratory scale operation. A method of viscometry was used to study the degradation behavior of aqueous dispersions of microgels. The experimental results show that the viscosity of polymer solution decreased with an increase in the ultrasonic irradiation time and approached a limiting value. The present work has enabled us to understand the role of the different operating parameters in deciding the extent of viscosity reduction in aqueous dispersions of microgels and also the controlling effects of them.

Branched Multifunctional Polyether Polyketals: Variation of Ketal Group Structure Enables Unprecedented Control over Polymer Degradation in Solution and within Cells

Multifunctional biocompatible and biodegradable nanomaterials incorporating specific degradable linkages that respond to various stimuli and with defined degradation profiles are critical to the advancement of targeted nanomedicine. Herein we report, for the first time, a new class of multifunctional dendritic polyether polyketals containing different ketal linkages in their backbone that exhibit unprecedented control over degradation in solution and within the cells. High-molecular-weight and highly compact poly(ketal hydroxyethers) (PKHEs) were synthesized from newly designed α-epoxy-ω-hydroxyl-functionalized AB(2)-type ketal monomers carrying structurally different ketal groups (both cyclic and acyclic) with good control over polymer properties by anionic ring-opening multibranching polymerization. Polymer functionalization with multiple azide and amine groups was achieved without degradation of the ketal group. The polymer degradation was controlled primarily by the differences in the structure and torsional strain of the substituted ketal groups in the main chain, while for polymers with linear (acyclic) ketal groups, the hydrophobicity of the polymer may play an additional role. This was supported by the log P values of the monomers and the hydrophobicity of the polymers determined by fluorescence spectroscopy using pyrene as the probe. A range of hydrolysis half-lives of the polymers at mild acidic pH values was achieved, from a few minutes to a few hundred days, directly correlating with the differences in ketal group structures. Confocal microscopy analyses demonstrated similar degradation profiles for PKHEs within live cells, as seen in solution and the delivery of fluorescent marker to the cytosol. The cell viability measured by MTS assay and blood compatibility determined by complement activation, platelet activation, and coagulation assays demonstrate that PKHEs and their degradation products are highly biocompatible. Taken together, these data demonstrate the utility this new class of biodegradable polymer as a highly promising candidate in the development of multifunctional nanomedicine.

3Pb4-12 Study of Degradation of Polymer in Solution at 20 kHz Sonication(Poster Session)

3Pb4-12 Study of Degradation of Polymer in Solution at 20 kHz Sonication(Poster Session)

2E-11 Frequency Dependence of Acoustic Degradation of Polymer in Solution(Physical Acoustics & Nonlinear & High-power Ultrasound, Sonochemistry)

2E-11 Frequency Dependence of Acoustic Degradation of Polymer in Solution(Physical Acoustics & Nonlinear & High-power Ultrasound, Sonochemistry)

Catalytic degradation of polybutadiene

The effect of Cobalt Fischer–Tropsch catalyst on the thermal degradation of cis-1,4 polybutadiene, polystyrene, chloride) and poly(vinyl acetate) in solution was investigated at various temperatures. The molecular weight distribution of the polymer was obtained by analyzing the samples by gel permeation chromatography. The catalyst enhanced the thermal degradation rate of polybutadiene in solution and had no effect on the thermal degradation of other polymers. However, the catalyst had no effect on the thermal degradation rate of polybutadiene in pyrolysis. Continuous distribution kinetics was used to evaluate the degradation rate coefficients for the thermal and catalytic degradation of polymers in solution. The activation energies, calculated from the temperature dependence of rate coefficients, were 130 kJ/mol and 108 kJ/mol for the thermal and catalytic degradation of polybutadiene in solution, respectively. The Friedman plot was used to determine the activation energy for the degradation of polybutadiene in pyrolysis.

Degradation kinetics of polymers in solution: Dynamics of molecular weight distributions

AbstractPolymer degradation occurs when macromolecular chains are broken under the influence of thermal, mechanical or chemical energy. Chain‐end depolymerization and random‐ and midpoint‐chain scission are mechanisms that have been observed in liquid‐phase polymer degradation. Here we develop mathematical models, unified by continuous‐mixture kinetics, to show how these different mechanisms affect polymer degradation in solution. Rate expressions for the fragmentation of molecular‐weight distributions (MWDs) govern the evolution of MWDs. The governing integrodifferential equations can be solved analytically for realistic conditions. Moment analysis for first‐order continuous kinetics shows the temporal behavior of MWDs. Chain‐end depolymerization yields monomer product and polymer molecular‐weight moments that vary linearly with time. In contrast, random‐ and midpoint‐chain scission models display exponential time behavior. The mathematical results reasonably describe experimental observations for polymer degradation. This approach, based on the time evolution of continuous distributions of chain length or molecular weight, provides a framework for interpreting several types of macromolecular degradation processes, particularly how bimodal MWDs can evolve during degradation.

Effect of Tetralin on the Degradation of Polymer in Solution

The effect of a hydrogen-donor solvent tetralin on thermal degradation of poly(styrene-allyl alcohol) in liquid solution was investigated in a steady-state tubular flow reactor at 1000 psig at various tetralin concentrations, polymer concentrations, and temperatures. The experimental data were interpreted with continuous- mixture kinetics, and rate coefficients determined for the specific and random degradation processes.

Continuous kinetics for thermal degradation of polymer in solution

AbstractContinuous kinetics of thermal degradation of poly (styrene‐allyl alcohol) (PSA) in solution are explored theoretically and experimentally. Thermal degradation experiments for PSA of number‐average molecular weight 1,640 in t‐butanol solution were conducted in a steady‐state flow reactor at 6.8 MPa and 403–473 K. The molecular‐weight distributions (MWDs) of the original polymer and its reaction products were measured as a function of residence time by gel permeation chromatography The MWD of the initial PSA is described by a gamma distribution function. Experimental data indicated that the polymer cracks to specific, low‐molecular‐weight (MW) products and degrades by random chain scission. Results are interpreted by a mathematical model based on the continuous kinetics for specific and random degradation processes. Rate coefficients are determined separately from the dynamic data of the MW moments for the specific products and the MWDs for the reacting polymer. Activation energies obtained are 5.9 – 7.4 kcal/mol for specific degradation processes and 35 kcal/mol for the random degradation process. The detailed MWDs are related to conventional lumped (numberaverage molecular‐weight) data.

New use of size exclusion chromatography in kinetics of mechanical degradation of polymers in solution

AbstractA new method to investigate the mechanical degradation of polymers in solution is described that uses size exclusion chromatograms of the initial polymer and of the degraded sample. The incipient parts of these chromatograms are analyzed to obtain kinetic data about degradation at the level of infinitesimal fractions. The procedure is based on the fact that mechanical degradation of the polymers is a first‐order reaction and macromolecules are cleaved mostly in their central region. The rate constant and the variation in the rate constant with molecular weight are determined in a single experiment, avoiding additional fractionation steps. Moreover, the slope of the size exclusion chromatographic calibration curve is derived, opening new ways to determine polydispersities or even to make rapid calibration for unknown polymers. To verify the method, the rate constant and the molecular weight dependence of the rate constant were determined for the sonic degradation of polystyrene in toluene. The rate constant is found to vary with the square of the molecular weight, and its value is in good agreement with results reported using much more laborious methods. © 1993 John Wiley & Sons, Inc.

Thermal and Oxidative Transformations of Polycyclohexadiene in the Solid Phase and Solution

Abstract The paper deals with the investigation of polycyclohexadiene oxidation mechanism in the solid phase and solution so as its inhibition. The schemes of these processes are proposed and kinetic parameters have been determined. Polymer degradation in solution is associated with transformation of peroxide radicals which lead to the formation of low-molecular products in the initial oxidation stage.

Degradation of polymer solutions in extensional flows

Degradation of polymer solutions in extensional flows

The kinetics of polymer degradation in solution—XIV. Radiolysis of poly(dimethyl itaconate)

Poly(dimethyl itaconate) (PDMI), underwent main-chain scission upon irradiation with 60Co-γ-rays or 16 MeV electrons in dilute 1,4-dioxane or acetone solution; crosslinking was not detected. In dilute 1,4-dioxane solution, a pronounced indirect radiation effect was found with G(S) p (related to the energy absorbed directly by the polymer) decreasing gradually from 4.8 to 2.3 scissions/100 eV for c PDMI increasing from 0.038 to 0.38 base mol/l. Pulse radiolysis experiments in conjunction with time-resolved light scattering measurements indicated at least two different intermediates, the decay of which resulted in main-chain scission. On the basis of results from quenching experiments with N 2O, the existence of a short-lived intermediate ( τ ⪡ 50 μsec), probably an electronically highly excited state resulting from the combination of electrons with positive ions, is suggested. Long-lived intermediates ( τ ≈ 3 msec) are attributed to lateral macroradicals formed by bond cleavage in the side groups. The decomposition of these radicals via main-chain scission was suppressed by O 2 and C 2H 5SH.

Theory of the mechanical degradation of polymers in solution by stirring. Size distribution after random scission

Cutting is performed at random on an arbitrary set of threads of sizes all greater than a predetermined length, a. The threads are cut at random until all become smaller than a, thus giving a distribution of sizes from zero to a. No thread will be cut further if its size is smaller than a. The size distribution is shown to be uniform. A more complicated case is considered in which pieces are cut at random until all are smaller than a but greater than m, such that m < 1 2 a . This case yields a final distribution which is uniform on [m, a-m], and decreases monotonically on [a-m, a]. The theory is applied to the scissions of polymers in solution by high speed stirring. Other possible applications are also discussed.

On the kinetics of polymer degradation in solution

Poly(2,2,2-trichloroethyl methacrylate), PTCMA, was irradiated in dilute dichloromethane solution with 16 MeV electron pulses of6 0Co γ-rays. Both in the presence and absence of O2, G(S)=9–10 was found at [PTCMA]<9 g/dm3. Indirect and direct radiation effects contributed to main-chain scission at a ratio of 7∶3. In contrast to earlier findings with dioxane solutions, at concentrations of up to 20 g/dm3 indications of crosslinking were not obtained. With CH2Cl2 solutions two modes of light scattering intensity (LSI) decrease were detected indicating the existence of two different macroradicals, one generated by the direct and the other by the indirect action of radiation. These radicals decayed with rate constants of 1.0·103 s−1 and 1.4·101 s−1 and also reacted with C2H5SH with rate constants of 8·104M−1·s−1 and 1·103M−1·s−1, respectively. In O2-saturated solutions both radicals formed peroxyl radicals, PO2, wich combined generating products whose decomposition involved main-chain scission. The combination of PO2-radicals was rate-determining in the consecutive series of reactions as inferred from the 2nd order decrease of the LSI.

On the kinetics of polymer degradation in solution—XII. Radiolysis of poly(2,2,2-trichloroethyl methacrylate)

The title compound (PTCMA) was irradiated in O 2-free dioxane solution by 60Co-γ-rays or by 100 nsec-pulses of 16 MeV electrons. At concentrations below ca 0.04 base mol/l, main-chain scission occurred as was concluded from the decrease of the light scattering intensity (LSI). G( S) = 3.7 ± 0.4 was independent of the polymer concentration and equal to G( S) observed with solid PTCMA. This result indicates that in dilute solution main-chain scission is induced by the direct action of radiation on the polymer. The free radical [presumably C(CH 3)(CH 2)] giving rise to main-chain scission has a lifetime of 2.6 msec. It reacts with ethane thiol (k = 6.6 × 10 4M −1sec −1). At concentrations above 0.04 base mol/l, the polymer crosslinked (gel formation, increase of the LSI according to 2nd order kinetics). It is assumed that crosslinking is due to the combination of radicals of the type CH 2C(CH 3)(COOCH 2CCl 2) formed via dissociative electron capture processes involving mainly electrons in spurs that otherwise recombine with parent ions. This conclusion was inferred from the finding that [( τ 1/2) 1] −1 ∞ ( c polymer) 2[( τ 1/2) 1): 1st half-life of LSI increase after the pulse, c polymer : polymer concentration].