Equilibrium Monomer Concentration Research Articles

Estimation of the chain propagation rate constants of propylene polymerization and ethylene‐1‐hexene copolymerization catalyzed with MgCl2‐supported Ziegler–Natta catalysts

AbstractIn olefin polymerization with MgCl2‐supported Ziegler–Natta (Z–N) catalysts, the apparent propagation rate constant (kp)a calculated by Rp = (kp)a [C*] CMe (CMe is equilibrium monomer concentration in the reaction system) declines with reaction time for gradually developed monomer diffusion limitation in the polymer/catalyst particles. In this work, a simplified multi‐grain particle model was proposed to build correlation between (kp)a and other kinetic parameters that can be determined experimentally. Rate profiles of propylene polymerization and ethylene‐1‐hexene copolymerization by three MgCl2‐supported Z–N catalysts were determined, and the (kp)a data was calculated using [C*] determined by quench‐labelling the propagation chains with acyl chloride. Decline of (kp)a in each polymerization process was precisely fitted by the linear correlation between lg(kp)a and [(ρcatmp)/(ρpmcat) + 1]1/3 developed on the particle model. Real propagation rate constant (kp) was estimated by extrapolating the fitting line to the starting point of polymerization, where no concentration gradient exists. According to the particle model, the slope of the lg(kp)a versus [(ρcatmp)/(ρpmcat) + 1]1/3 line (lgd) represents the degree of monomer diffusion limitation. Variations of parameter d found in the studied reaction systems can be reasonably explained based on the knowledge of olefin diffusion in the polymer phase.

Room-Temperature Grafting from Synthesis of Protein-Polydisulfide Conjugates via Aggregation-Induced Polymerization.

The reversible modification of proteins with lipoic acid (LPA)-derived polydisulfides (PDS) is an important approach toward the transient regulation and on-demand recovery of protein functions. The in situ growth of PDS from the cysteine (Cys) residue of a protein, however, has been challenging due to the near-equilibrium thermodynamics of the ring-opening polymerization of LPA. Here, we report the protein-mediated, aggregation-induced polymerization (AIP) of amphiphilic LPA-derived monomers at room temperature, which can be performed at a concentration as low as ∼2% of the equilibrium monomer concentration normally needed. The aggregation of monomers increases the effective monomer concentration in aqueous solutions to the degree that the polymerizations behave similarly to those in bulk. The PDS conjugation enhances the thermostability, protease resistance, and tolerance to freeze-thaw treatments of the target proteins. Moreover, the PDS conjugation allows rapid and convenient purification of Cys-bearing proteins by taking advantage of the liquid-liquid phase separation of the protein-PDS conjugates and the full recovery of native proteins under mild reducing conditions. This AIP effect may shed light on facilitating other polymerizations with a similar near-equilibrium character. The PDS conjugation can open up new avenues to protein delivery, dynamic and reversible protein engineering, enzyme preservation, and recycling.

Living polymerization in nano-scale volumes. Impact of process conditions on polymerization kinetics and product characteristics

Living polymerization processes, irreversible and reversible, proceeding in a large number of isolated (no mass exchange) nano-scale reactors (droplets) were modeled using stochastic (Monte Carlo) and deterministic simulations and analytical solutions of derived mathematical equations. Monomer and living unimer used as initiator were redistributed in droplets uniformly or accordingly to the Poisson distribution, resulting in nanoreactors containing a small number of growing chains. Stochasticity of reactions involving low number of molecules affects the concentration of monomer and chain length distributions in individual droplets, both differing from ones accounted in macroscopic system. The developed mathematical description, based on values of rate constants of propagation (kp) and depropagation (kd) reactions and on initial monomer and living unimer concentrations, as well as numerical simulations, allow predicting kinetics of the process and of several characteristics of the products resulting therefrom, e.g. chain length distribution. Moreover, they allow also following evolution of droplet subpopulations that differ in composition. Moreover, for the reversible process the equilibrium monomer concentration in a droplets system [M]eq can be calculated. As living ionic and coordination polymerization and the controlled radical polymerization in nano-scale dispersions are rather little explored the theoretical predictions shown in this work could facilitate their further development.

A Thermodynamic Roadmap for the Grafting-through Polymerization of PDMS11MA.

Grafting-through atom transfer radical polymerization (ATRP) was used to polymerize a sterically hindered poly(dimethylsiloxane) methacrylate (PDMS11MA, Mn = 1000) macromonomer to high conversion as a function of temperature, solvent, initial monomer concentration, and pressure. Higher polymerization yields were obtained when polymerizations were conducted at (i) lower temperature (T), (ii) in a poor solvent for the side chain, (iii) higher initial monomer concentration ([M]0), and (iv) higher pressure by mitigating the contribution of the equilibrium monomer concentration ([M]eq). The enthalpy of polymerization (ΔHp) and entropy of polymerization (ΔSp) were more negative in poor solvents. Polymerizations at ambient pressure required higher [M]0, use of a poor solvent, and lower temperatures to reach higher conversion with good control, whereas high pressure ATRP (HP-ATRP) displayed better control under dilute conditions. Grafting-through polymerization at high P and higher [M]0 was less controlled, plausibly due to limited solubility and mobility of the copper catalyst in the highly viscous medium.

Poor Solvents Improve Yield of Grafting-Through Radical Polymerization of OEO19MA.

Radical polymerization of poly(ethylene glycol) methyl ether methacrylate (OEO19MA, Mn ∼ 950) at an initial monomer concentration of 150 mM was investigated as a function of solvent composition. Conventional and controlled radical polymerizations in anisole at 60 °C converged at approximately the same equilibrium monomer concentration ([M]eq) of ∼38 mM, suggesting that livingness or diminished termination did not affect the thermodynamic parameters of polymerization. Conventional radical polymerizations (RPs) in anisole, dimethylformamide (DMF), toluene, and 1×PBS buffered water were taken to approximately 98% thermal initiator decomposition to determine [M]eq at reaction completion within a broad temperature range. The enthalpy (ΔHp) and entropy (ΔSp°) of polymerization were solvent-dependent. Polymerizations in 1×PBS were the most thermodynamically favorable, followed by those in DMF, toluene, and anisole. -ΔHp and -ΔSp increased with the square of the difference in the Hansen solubility parameters of poly(ethylene glycol) and the solvent. It is proposed that poor solvents favor polymer-polymer interactions over polymer-solvent interactions, which improves the thermodynamic polymerizability.

Controlled radical depolymerization of chlorine-capped PMMA via reversible activation of the terminal group by ruthenium catalyst

This paper deals with a preliminary study in controlled radical depolymerization, that is a unimodal polymer is converted into monomer while maintaining the narrow molecular weight distribution. Thus, our effort has been directed to unzipping-type depolymerization triggered by the reversible activation of the terminal group. An indenyl-based ruthenium catalyst afforded depolymerization of a chlorine-capped poly(methyl methacrylate) (PMMA-Cl) at relatively high temperature (>100 °C). Interestingly, the SEC curve shifted to lower molecular weight as the time proceeds, and the monomer, that is MMA, definitely generated and the amount almost corresponded to the decrease in molecular weight. The depolymerization was eventually saturated due to the equilibrium monomer concentration, but evaporation of the generating monomer followed by an addition of solvent and re-heating allowed further progress of depolymerization. We have thus demonstrated four consecutive depolymerizations via the evaporation methodology resulting in the unimodal SEC curve shift to lower molecular weight.

Ring‐Opening Metathesis Copolymerization of Cyclopentene Above and Below Its Equilibrium Monomer Concentration

AbstractCyclopentene (C) and norbornene (N) may both be enchained by ring‐opening metathesis polymerization (ROMP). N homopolymerizes to essential completion, but C has a significant equilibrium monomer concentration, [C]eq = 1.17 m at 30 °C. While C cannot homopolymerize below [C]eq, it can still be enchained in copolymerizations with N. A terminal kinetic model, where one monomer shows depropagation competitive with propagation, well represents experimental data for the “living” ROMP copolymerization of C and N with a Mo‐based “Schrock‐type” initiator, covering a broad range of monomer feed ratios, both above and below [C]eq. Incorporating a penultimate unit effect on C depropagation increases the model's accuracy when both the monomers are dilute. Below [C]eq, polymerization halts when all N is consumed; above [C]eq, a C homopolymer block forms once all N is consumed. As polycyclopentene may be hydrogenated to linear polyethylene, such copolymerizations offer a facile route to polyethylene‐containing block copolymers from a single charge of mixed‐monomer feed.

Synthesis of Poly(OEOMA) Using Macromonomers via “Grafting-Through” ATRP

Atom transfer radical polymerization (ATRP) of oligo(ethylene oxide) methyl ether methacrylate (OEOMA, Mn = 950 or 2080; OEOMA is also termed poly(ethylene glycol) methyl ether methacrylate, PEGMA) macromonomers was investigated as a function of initial monomer concentration, [OEOMA]0, ranging from 50 to 300 mM, and up to 4.5 kbar. Polymerizations were successfully carried out in organic solvents with [OEOMA]0 > 75 mM, whereas with [OEOMA]0 = 50 mM no monomer conversion was observed at ambient pressure, indicating that the macromonomer concentration was below its equilibrium monomer concentration ([M]e). High pressure reduced [M]e to a level lower than under ambient pressure, allowing polymerization at [OEOMA]0 = 50 mM up to high monomer conversion and yielding polymers with narrow molecular weight distribution. By varying the targeted degree of polymerization of OEOMA, brushlike or starlike poly(OEOMA) were prepared under both ambient and high pressure.

Real-time monitoring of living cationic ring-opening polymerization of THF and direct prediction of equilibrium molecular weight of polyTHF

A convenient real-time monitoring of monomer concentration during living cationic ring-opening polymerizations of tetrahydrofuran (THF) initiated with methyl triflate (MeOTf) has been developed for kinetic investigation and determination of equilibrium monomer concentration ([M]e) via in situ FTIR spectroscopy in combination with a diamond tipped attenuated total reflectance (ATR) immersion probe. The polymerization rate was first order with respect to monomer concentration and initiator concentration from the linear slope of ln([M]0-[M]e)/([M]-[M]e) versus polymerization time at different temperatures in various solvents. [M]e decreased linearly with initial monomer concentration while increased exponentially with increasing polymerization temperature. The equilibrium also strongly depends on solvent polarity and its interaction with monomer. The equilibrium polymerization time (t e) decreased with increasing solvent polarity and decreased linearly with increasing [M]0 in three solvents with different slopes to the same point of bulk polymerization in the absence of solvent. Equation of M n,e = 72.1/(0.14-0.04[M]e) has been established to provide a simple and effective approach for the prediction for the number-average molecular weight of polyTHFs at equilibrium state (M n,e) in the equilibrium living cationic ring-opening polymerization of THF at 0 °C.

Kinetics of micellisation and relaxation of cylindrical micelles described by the difference Becker–Döring equation

A numerical description of micellisation and relaxation to an aggregate equilibrium in a nonionic surfactant solution with spherical premicellar aggregates and stable polydisperse cylindrical micelles is presented for a wide interval of total surfactant concentrations and initial conditions. The Smoluchowsky-type model for the attachment-detachment rates of surfactant monomers to and from surfactant aggregates with matching rates for small spherical premicellar aggregates and the rates for larger cylindrical micelles have been used. The full discrete spectrum of characteristic times of micellar relaxation and the first three relaxation modes in their dependence on the equilibrium monomer concentration have been computed using the linearized form of the Becker-Döring difference equations. The overall time behavior of the surfactant monomer and aggregate concentrations in micellisation and relaxation at large initial deviations from the final equilibrium has been studied with the help of nonlinearized discrete Becker-Döring kinetic equations. The studies demonstrate a possibility for non-monotonic evolution of the monomer concentration at the initial stages. A comparison of the computed results with the analytical ones known from solutions of the linearized and nonlinearized differential Becker-Döring kinetic equations demonstrates a general agreement at higher concentrations of the surfactant above the critical micellar concentration.

Ring-opening polymerization of a five-membered lactone trans-fused to a cyclohexane ring

The ring-opening polymerization behavior of five-membered lactones fused to a cyclohexane ring (that is, the trans- and cis-hexahydro-2(3H)-benzofuranone denoted T6L and C6L, respectively) was investigated under various conditions. The potassium tert-butoxide (tBuOK)-initiated anionic polymerization of T6L yields polymers with number-average molecular weight (Mn) values of 5000. However, no polymeric products were obtained via cationic and coordination polymerization. Among the anionic initiators, a base stronger than an alkoxide initiated the polymerization of T6L. In contrast, cis-isomer C6L did not polymerize regardless of the initiator species used, which implied an increase in the ring strain of the lactone ring by the trans-fused cyclohexane. The anionic polymerization of T6L was reversible, and the thermodynamic parameters characterizing the polymerization of T6L were estimated to be ΔHp°=−18 kJ·mol−1 and ΔSp°=–65 J·K−1mol−1 on the basis of the measurement of the equilibrium monomer concentration. The ring-opening polymerization behavior of five-membered lactones fused to a cyclohexane ring, T6L and C6L, was investigated under various conditions. The t-BuOK-initiated anionic polymerization of T6L produces polymers having Mn values of 5000. In remarkable contrast, C6L did not polymerize at all, implying the increase in ring strain of the lactone ring by trans-fused cyclohexane. The anionic polymerization of T6L was reversible, and the thermodynamic parameters characterizing the polymerization of T6L were estimated to be ΔHp°=−18 kJ·mol−1 and ΔSp°=–65 J·K−1mol−1.

Micellization and relaxation in solution with spherical micelles via the discrete Becker–Döring equations at different total surfactant concentrations

A numerical description of micellization and relaxation to an aggregate equilibrium in surfactant solution with nonionic spherical micelles has been developed on the basis of a discrete form of the Becker-Döring kinetic equations. Two different models for the monomer-aggregate attachment-detachment rates have been used, and it has been shown that the results are qualitatively the same. The full discrete spectrum of characteristic times of micellar relaxation and first relaxation modes in their dependence on equilibrium monomer concentration have been found with using the linearized form of the Becker-Döring kinetic equations. Overall time behavior of surfactant monomer and aggregate concentrations in micellization and relaxation at large initial deviations from final equilibrium has been studied with the help of nonlinearized discrete Becker-Döring kinetic equations. Comparison of the computed results with the analytical ones known in the limiting cases from solutions of the linearized and nonlinearized continuous Becker-Döring kinetic equation demonstrates general agreement.

Bulk Ring-Opening Transesterification Polymerization of the Renewable δ-Decalactone Using an Organocatalyst.

The bulk ring-opening polymerization of renewable δ-decalactone using 1,5,7-triazabicyclo[4.4.0]dec-5-ene was carried out at temperatures between 7 and 110 °C. The equilibrium monomer concentration for reactions within this temperature range was used to determine the polymerization thermodynamic parameters (ΔHp = -17.1 ± 0.6 kJ mol-1, ΔSp = -54 ± 2 J mol-1 K-1) for δ-decalactone. The polymerization kinetics were established and high molar mass poly(δ-decalactone) was prepared with a glass transition temperature of -51 °C. Poly(δ-decalactone) samples with controlled molar mass and narrow molar mass distributions were realized by controlling the monomer conversion and initiator concentration. A high molar mass poly(lactide)-poly(δ-decalactone)-poly(lactide) triblock copolymer with a low polydispersity index was prepared by simple sequential addition of monomers. The product triblock exhibited two distinct glass transitions temperatures consistent with microphase segregation.

Catalytic Polymerization of a Cyclic Ester Derived from a “Cool” Natural Precursor

(-)-Menthide, a seven-membered lactone derived from the natural product (-)-menthol, was polymerized using a structurally defined zinc-alkoxide catalyst to form an aliphatic polyester. The polymer was fully characterized by NMR spectroscopy, size exclusion chromatography, and matrix-assisted laser desorption ionization mass spectrometry. The polymerization reaction occurred in a controlled fashion and polymer samples with M(n) values up to 90 kg mol(-1) were obtained by varying the catalyst loading. Monitoring of the rate of polymerization by in situ FT-IR spectroscopy (ReactIR) revealed a first order dependence on (-)-menthide. The temperature dependence of the observed rate constant between 30 and 90 degrees C was well described by the Arrhenius equation and gave E(a) = 38.4 +/- 0.9 kJ mol(-1). Thermodynamic parameters (deltaH(p) degrees = -16.8 +/- 1.6 kJ mol(-1), deltaS(p) degrees = -27.4 +/- 4.6 J mol(-1) K(-1)) for the polymerization of (-)-menthide were also determined by measuring the equilibrium monomer concentration at different temperatures ranging from 40 to 100 degrees C. The equilibrium monomer concentrations at 25 and 100 degrees C were calculated to be 0.031 +/- 0.018 and 0.120 +/- 0.063 M, respectively.

Copolymerization of ll-Lactide at Its Living Polymer−Monomer Equilibrium with ε-Caprolactone as Comonomer

Introduction. Copolymerization of a given monomer, after it has reached equilibrium with its homopolymer, is a well-known general phenomenon and was studied in the past by several authors.1-8 The monomer in equilibrium may interact either stronger or weaker with a foreign active center than with its own. In the former instance its equilibrium monomer concentration ([M]eq) would decrease, whereas in the latter no effect on [M]eq would be observed. The pertinent equations describing the dependence of the copolymer composition on the monomer feed have also been derived in the past for several systems.9 Thermodynamic treatments of such instances have been summarized in the extensive Sawada’s monograph1 and the chapter devoted to thermodynamics of the ring-opening polymerization in Comprehensive Polymer Science.10 However, we could not find in the available open literature any study of specific copolymerization with the aim of introducing a given monomer into a polymer after living polymermonomer equilibrium was reached. It is shown in the present paper that LL-lactide (LA) can be completely converted into polymer repeating units with the help of another monomer. This is important because the six-membered LA, as well as some other medium-strained cyclic esters, has relatively high equilibrium monomer concentrations, increasing with the increasing polymerization temperature.11-13 Since polymerization of LA is conducted often in the monomer/polymer melt, relatively high temperatures are required. In our earlier work, devoted to the thermodynamics of LA polymerization, the corresponding dependence of the equilibrium LA concentration ([LA]eq) on temperature was found, and then the enthalpy (∆Hlc) and entropy (∆S°lc) of the LA monomer to polymer transformation were determined.11 For instance, at 180 °C, i.e., close to the polymer melting point, [LA]eq is equal to 0.32 mol L-1. It is therefore important to find conditions to force this monomer, being in a relatively high equilibrium concentration, to enter into the polymer chains. If lowering of the polymerization temperature cannot be applied, copolymerization looks to be the only way to achieve this goal. Indeed, lowering temperature and polymer crystallization would decrease the amount of monomer at equilibrium, but remelting of the system at higher temperature would restate the previous conditions. When copolymerization is applied, the repeating units derived from a comonomer will appear at the polymer chain end that would alter in a certain way the final polymer properties. Thus, the comonomer structure has to be chosen in a way preventing deterioration of the properties as little as possible. In another series of papers from this laboratory and related to another system of the ring-opening polymerization, it has been shown that when equilibrium is reached, it is possible by proper comonomer choice to form a periodic or alternating copolymer, depending on the structures of the given comonomers pair.7,8 Results and Discussion. In this preliminary communication we show that LA is able to copolymerize with -caprolactone (CL) at or below its monomer equilibrium concentration ([LA]eq) reached in homopolymerization. We also show that even CL, known to have much lower reactivity than LA in their copolymerization carried out above equilibrium concentration for both comonomers,14 enters even faster the chains than LA when [LA]eq is reached. This phenomenon has a thermodynamic origin since LA addition to the active polymer chains bearing a terminal lactide unit is counterbalanced by depropagation (thus, cannot form longer sequences). Therefore, whenever the ...-la* chain end is formed, the probability of formation of the ...-la-cl* unit prevails over that of ...-la-la*. It does not mean that the formation of the ...-la-la* unit is slower than formation of the ...-la-cl* unit (thus, LA is still more reactive monomer), but ...-la-la* depropagates much faster than the ...-la-cl* does.

Comprehensive Analysis of Single-Particle Growth in Heterogeneous Olefin Polymerization: The Random-Pore Polymeric Flow Model

In the present study, a comprehensive mathematical model is developed to analyze the effects of initial catalyst size, active site concentration, catalyst morphology (e.g., porosity, extent of prepolymerization, etc.), and hydrodynamic conditions on the growth and overheating of highly active Ziegler−Natta catalyst particles (e.g., fresh or prepolymerized) in gas-phase olefin polymerization. The generalized Stefan−Maxwell diffusion equation for porous solids is combined with the mass balances on the various molecular species (i.e., monomer and “live” and “dead” polymer chains) and the energy conservation equation to predict the temporal−spatial evolution of temperature and monomer concentration, as well as the polymerization rate in a single catalyst/polymer particle. To calculate the equilibrium monomer concentration in the amorphous polymer phase, the Sanchez−Lacombe equation of state is employed. It is shown that the evolution of the catalyst/particle morphology greatly affects the internal and externa...

Monomer−Linear Macromolecules−Cyclic Oligomers Equilibria in the Polymerization of 1,4-Dioxan-2-one

1,4-Dioxane-2-one (DX) was polymerized in 1,4-dioxane as solvent or in bulk by means of the tin octoate/butyl alcohol (Sn(Oct)2/BuOH) mixture as an initiating system, in the range of temperatures from 80 to 120 °C. Size exclusion chromatography (SEC) and MALDI TOF mass spectrometry measurements of the crude reacting mixtures revealed that in the thermodynamically equilibrated systems a relatively high fraction of cyclic oligomers (DX(i)) appear. The molar concentration of cyclic oligomers (∑i[DX(i)]eq) increased with increasing temperature and monomer concentration in the feed and reached a maximum value equal approximately to 1 mol L-1 for the polymerization in bulk. On the other hand, the mass fraction (f) of cyclic oligomers after passing a maximum (f = 40% at [DX]0 ≈ 4.0 mol L-1, 100 °C) decreased with increasing [DX]0, and eventually for bulk polymerization f < 10% (f = 8% at 80 °C) was reached. The equilibrium monomer concentration, determined by means of SEC, increased with increasing [DX]0 until [...

Studies of higher temperature polymerization ofn-butyl methacrylate andn-butyl acrylate

Free-radical acrylic polymerizations of n-butyl methacrylate and n-butyl acrylate at temperatures above 120°C show significant departure from classic free-radical kinetics. An extended model of depropagation, where the equilibrium monomer concentration varies with temperature and polymer content, is postulated and shown to adequately explain the data for n-butyl methacrylate. Intramolecular chain transfer and scission is postulated to explain the apparent reduction in molecular weight and rate of polymerization seen in n-butyl acrylate polymerization, with supporting experimental evidence found via electrospray-ionization mass spectrometry.

Controlled Ring-Opening Polymerization of Lactones and Lactides Initiated by Lanthanum Isopropoxide, 1. General Aspects and Kinetics

Ring-opening polymerization of various lactones and lactides initiated by lanthanum isopropoxide has been investigated. Analysis of molecular weights and molecular-weight distributions of the resulting polymers shows that the ring-opening process is a controlled reaction, which is initiated by a variable number of isopropoxy groups. This number depends on both the monomer and the [monomer]/[initiator] ratio. Kinetic studies indicate that all the polymerizations are equilibrated, and the corresponding thermodynamic parameters and the equilibrium monomer concentrations have been calculated. Comprehensive kinetics carried out for e-caprolactone abd δ-valerolactone polymerizations allows the determination of kinetic order relative to both monomer and initiator concentrations, along with that of the apparent rate constants of polymerization. It is also demonstrated that propagation occurs on aggregated (δ-valerolactone) or unaggregated (e-caprolactone) active polymer chains and that the ring-opening process proceeds via [O-acyl] bond cleavages.

Perfectly Alternating Copolymer of Lactic Acid and Ethylene Oxide as a Plasticizing Agent for Polylactide

The ring-opening polymerization of 3-methyl-1,4-dioxan-2-one (MDO) mediated by a catalytic system composed of Y[N(TMS)2]3 and benzyl alcohol (BnOH) led to a new polymer (PMDO) comprised of perfectly alternating lactic acid and ethylene oxide repeat units. Samples of PMDO were characterized by NMR spectroscopy, size exclusion chromatography (SEC), and matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). In a series of MDO polymerizations ([MDO]0 = 3.0 M in toluene, between −30 and 60 °C), the equilibrium monomer concentrations were measured. The thermodynamic parameters for the polymerization reaction were determined: ΔHp° = −12.1 ± 0.5 kJ mol-1 and ΔSp° = −42 ± 2 J mol-1 K-1. The glass transition temperature (Tg) of PMDO was determined to be ≈−24 °C by differential scanning calorimetry and found to vary little over the molecular weight range studied (3−21 kg/mol). Mixtures of low-molecular-weight PMDO and atactic polylactide (PLA) were prepared by solution casting and subsequent annealing significantly above the Tg's of the individual components. Miscibility of PLA and PMDO was evinced by single Tg's that were well-described by the Fox relationship for miscible blends. Because of its miscibility with PLA and low Tg, PMDO has potential as a macromolecular plasticizing agent for commercially relevant PLA.