Molar Mass Poly Research Articles

Preparation of Poly(acrylate)/Poly(diallyldimethylammonium) Coacervates without Small Counterions and Their Phase Behavior upon Salt Addition towards Poly-Ions Segregation.

In this work, we report the phase behavior of polyelectrolyte complex coacervates (PECs) of poly(acrylate) (PA−) and poly(diallyldimethylammonium) (PDADMA+) in the presence of inorganic salts. Titrations of the polyelectrolytes in their acidic and alkaline forms were performed to obtain the coacervates in the absence of their small counterions. This approach was previously applied to the preparation of polymer–surfactant complexes, and we demonstrate that it also succeeded in producing complexes free of small counterions with a low extent of Hofmann elimination. For phase behavior studies, two different molar masses of poly(acrylate) and two different salts were employed over a wide concentration range. It was possible to define the regions at which associative and segregative phase separation take place. The latter one was exploited in more details because the segregation phenomenon in mixtures of oppositely charged polyelectrolytes is scarcely reported. Phase composition analyses showed that there is a strong segregation for both PA− and PDADMA+, who are accompanied by their small counterions. These results demonstrate that the occurrence of poly-ion segregation in these mixtures depends on the anion involved: in this case, it was observed with NaCl, but not with Na2SO4.

Synthesis and characterization of poly (acrylonitrile-g-lignin) by semi-batch solution polymerization and evaluation of their potential application as carbon materials

Understanding the factors that govern the graft polymer structure is of central importance to the development of technologies for converting polymers into carbon materials. In this work, poly (acrylonitrile-g-lignin) was synthesized by one-pot semi-batch solution polymerization of acrylonitrile (AN) with different amounts of Kraft lignin (KL), aiming the carbon materials producing. The synthesis process parameters to obtain poly (acrylonitrile-g-lignin) hybrid polymers from different KL contents were optimized. The purpose of this work was to substitute part of the AN by KL, with the KL amount varying from 0 to 35 wt.% in the copolymer and to investigate the consequent effects on the grafting percent, viscosity, overall monomer conversion, molar masses, thermal properties and carbon yield. The results obtained show the success in preparation of the grafted polymers with KL and that this insertion improved the thermal stability of the polymers and the carbon yield. The molar masses of poly (AN-g-KL) showed direct relationship with the amount of KL used and the grafting percentage. The results showed that the grafting percentage and viscosity of solutions decreases as the concentration of KL increased. The molar mass results and thermal properties showed a direct relationship to the KL concentration in the synthesized copolymer. Among the proportions of AN/KL studied, the copolymer 75/25 (P-25KL) presented the most promising results for application as carbon material precursor.

Direct access to poly(glycidyl azide) and its copolymers through anionic (co-)polymerization of glycidyl azide

Glycidyl azide polymer or poly(glycidyl azide) which is considered as an excellent energetic binder or plasticizer in advanced solid propellants is generally obtained by post-modification or azidation of poly(epichlorohydrin). Here we report that glycidyl azide can be directly homopolymerized through anionic ring-opening polymerization to access poly(glycidyl azide) using onium salts as initiator and triethyl borane as activator. Molar masses of poly(glycidyl azide) up to 11.0 Kg/mol are achieved in a controlled manner with a narrow polydispersity index (PDI ≤ 1.2). Similarly, alternating poly(glycidyl azide carbonate) are also prepared through alternating copolymerization of glycidyl azide with carbon dioxide. Lastly, the copolymerization of glycidyl azide with other epoxide monomers is carried out; the azido functions carried by glycidyl azide which are successfully incorporated into the backbones of polyethers and polycarbonates based on cyclohexene oxide and propylene oxide subsequently served to introduce other functions by click chemistry.

Modeling of elementary reactions and kinetics of radical‐initiated methyl methacrylate polymerization in the presence of ferrocene

AbstractOn the basis of quantum chemical modeling, a kinetic scheme of methyl methacrylate polymerization initiated by benzoyl peroxide in the presence of ferrocene was proposed. The process runs by mechanism, which includes the reactions of free radical polymerization, and the reactions leading to formation and operability of two type coordination active sites that are capable of converting into each other. On the basis of the proposed scheme, a kinetic model was developed. This model quantitatively described the following: the experimentally determined time dependences of the methyl methacrylate conversion, the conversion dependencies of the number‐average and weight‐average molar masses of poly(methyl methacrylate), the stereoregularity values of poly(methyl methacrylate), and the time dependencies of the methyl methacrylate conversion upon its polymerization on poly(methyl methacrylate) macroinitiators obtained in radical‐initiated polymerization in the presence of ferrocene. As a result of solving the inverse kinetic problem, the parameters of temperature dependences of the reaction rate coefficients of the proposed kinetic scheme were found.

The influence of initiator and macrocyclic ligand on unsaturation and molar mass of poly(propylene oxide)s prepared with various anionic system

Anionic polymerization of propylene oxide was carried out in the presence of two groups of potassium salts activated 18-crown-6 (18C6), e.g. alkoxide salts (CH3OK, i-PrOK, t-BuOK, CH3OCH2CH(CH3)OK, KCH2O) and other salts (CbK, Ph3CK, Ph2PK, Ph3HBK, KK, KH, and [(CH3)3Si]2NK) in THF at room temperature. Application of various initiating systems results in polyethers which are different in level and kind of unsaturation represented by allyloxy, cis- and trans-propenyloxy, as well as vinyloxy starting groups. In the presence of selected initiator, i.e. t-BuO−K+ unsaturation increases markedly by addition of 18C6 or C222. During the initiation step oxirane ring-opening and direct deprotonation of the monomer occur simultaneously involving in some cases also the ligand. All initiators opens oxirane ring in the β-position except i-PrOK, which opens it in the β- and α-position. The mechanisms of the reactions were discussed.

Organic Lewis Pairs Based on Phosphine and Electrophilic Silane for the Direct and Controlled Polymerization of Methyl Methacrylate: Experimental and Theoretical Investigations

Fully organic Lewis pairs, combining a phosphine such as tri-n-butylphosphine (PnBu3), tritert-butylphosphine (PtBu3) or tris(2,4,6-trimethoxyphenyl) phosphine (TTMPP) as a Lewis base, and N-(trimethylsilyl)bis(trifluoromethane sulfonyl)imide (Me3SiNTf2) as a Lewis acid, are shown to directly initiate the polymerization of methyl methacrylate (MMA) at room temperature in toluene. A dual reaction mechanism involving an optimal TTMPP:Me3SiNTf2 ratio of 1:2 accounts for the control of the polymerization. Molar masses of poly(methyl methacrylate)’s (PMMA’s) can be varied by the initial [MMA]0/[TTMPP]0 molar ratio. Chain extension experiments confirm that a majority of chains of a TTMPP/Me3SiNTf2-derived PMMA can be reactivated. Both density functional theory (DFT) calculations and stoichiometric studies reveal that TTMPP and Me3SiNTf2 form a P-silyl phosphonium intermediate that is in equilibrium with the corresponding frustrated Lewis pair (FLP). This FLP could correspond to the active form of the initiation...

Photoinduced controlled/“living” polymerization of methyl methacrylate with flavone as photoinitiator

ABSTRACTPhotochemically mediated controlled/“living” polymerization of methyl methacrylate (MMA) triggered by flavone was studied. The polymerization was performed in ethanol at ambient temperature with CuBr2/Tris(2‐dimethylaminoethyl)amine (Me6TREN) as complex catalyst and ethyl 2‐bromoisobutyrate (EBiB) as initiator. The molar mass of poly(methyl methacrylate) (PMMA) was obtained and exhibited relatively narrow molecular weight distribution (Mw/Mn) which was characterized by gel permeation chromatography (GPC). Chain extension further indicated that the living nature was maintained in the photopolymerization system. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43845.

Toughening Glassy Poly(lactide) with Block Copolymer Micelles.

Poly(lactide) (PLA), a compostable bioderived polyester, can be produced at a cost and scale that makes it an attractive replacement for nondegradable petroleum-derived thermoplastics. However, pristine PLA is brittle and unsuitable for use in applications where high impact strength and ductility are required. In this work we demonstrate that poly(l-lactide) (PLLA) in the glassy state can be toughened significantly via addition of an amphiphilic diblock polymer. Notably, a PLLA blend containing only 5 wt% poly(ethylene oxide)-b-poly(butylene oxide) (PEO-PBO) exhibited tensile toughness and notched Izod impact strength over an order of magnitude higher than neat amorphous PLLA without a significant reduction in transparency or elastic modulus. For a series of PLLA blends containing PEO-PBO of fixed composition (∼70% volume fraction PBO), the toughness was inversely related to the molar mass of the added modifier with the highest toughness observed for the blend containing the smallest diblock (∼7 kg/mol). Interestingly, at fixed composition and molar mass poly(l-lactide)-b-poly(butylene oxide) (PLLA-PBO) exhibited a substantial but reduced toughening efficiency compared to PEO-PBO. We attribute this difference to a change in the solubility parameter of the amphiphilc block. Using TEM, we show that the greatest toughening is observed when the diblock modifier forms small cylindrical micelles that are well dispersed in the PLLA matrix. This morphology is facilitated by a negative Flory-Huggins interaction parameter (χ) between PEO and PLLA. These insights suggest a new and versatile strategy for the facile and efficient toughening of brittle thermoplastics.

The Influence of Crown Ether and Alcohol on Unsaturation and Molar Mass of Poly(propylene oxide)s Prepared by Use of Potassium t-Butoxide: Reinvestigation of Chain Transfer Reactions.

Potassium t-butoxide dissolved in tetrahydrofuran effectively initiates homogeneous polymerization of propylene oxide at room temperature. Unsaturation and molar mass (M n) of the polymers prepared depend on the presence of additives, such as macrocyclic ligand 18-crown-6 (L) and t-butanol. Application of the ligand alone results in distinct increase of unsaturation and decrease of M n, whereas use of t-BuOH leads to simultaneous decrease of unsaturation and M n. Activation of t-BuOK/t-BuOH system with the ligand causes further decrease of unsaturation, that is, from 12.0 to 3.5 mol % for OK/OH (1/3) and OK/OH/L (1/3/2) systems, respectively. Unexpectedly, M n of the polymers obtained does not practically change (~4800). This result differs from that reported earlier for neat PO polymerization initiated potassium 1-methoxy-2-propoxide/1-methoxy-2-propanol, in which in the presence of the same ligand M n increases to ~12 400 for the same ratio of reagents. The mechanism of studied processes was discussed.

Kinetics of RAFT homopolymerisation of vinylbenzyl chloride in the presence of xanthate or trithiocarbonate

The RAFT homopolymerisation of vinylbenzyl chloride (VBC, or chloromethyl styrene CMS) in bulk and in acetonitrile initiated by α,α′-azoisobutyronitrile (AIBN) in the presence of two chain transfer agents, O-ethyl-S-(1-methyloxycarbonyl)ethyl xanthate and dibenzyl trithiocarbonate, is presented. The reactions were monitored by 1H nuclear magnetic resonance spectroscopy in the presence of 1,2-dichloroethane as the internal standard. Such a technique enabled one to assess the evolutions of log([M]0/[M]) and VBC conversion vs. time that were shown to be linear. Tobolsky’s law allowed one to determine the square of the propagation rate constant to the termination rate constant, kp2/kte, of VBC, that worths about 3×10−3lmol−1s−1 at 80°C. On the one hand, the controlled character of the polymerisation involving dibenzyl trithiocarbonate was confirmed by size exclusion chromatography. On the other hand, the molar masses of poly(VBC) polymerised in the presence of the xanthate agent decreased with monomer conversion, as already stated with the macromolecular design via interchange of xanthates (MADIX) polymerisation of styrene.

Soybean peroxidase‐catalyzed treatment and removal of BPA and bisphenol derivatives from aqueous solutions

AbstractThe systematic studies were carried out to determine the optimum process parameters, such as the hydrogen peroxide (H2O2) concentration, concentration and molar mass of poly(ethylene glycol) (PEG) as an additive, pH value, temperature, and enzyme dose for treatment of bisphenol A (BPA) with soybean peroxidase (SBP). The SBP‐catalyzed treatment of BPA was effectively enhanced by adding PEG in the presence of H2O2. BPA was completely treated by SBP of 0.50 U/cm3 and water‐insoluble oligomers were generated. The optimum conditions for SBP‐catalyzed treatment of BPA at 0.3 mM were determined to be 0.3 mM of H2O2 and 0.10 mg/cm3 of PEG with molar mass of 1.0 × 104 g/mol in a pH 7.0 buffer at 30°C. A variety of bisphenol derivatives were completely or effectively treated by SBP under the optimum conditions determined for treatment of BPA, although the SBP dose was further increased as necessary for some of them. The aggregation of water‐insoluble oligomers generated was enhanced by decreasing the pH values of the solutions to 4.0 with HCl after the enzymatic treatment, and BPA and bisphenol derivatives were removed from aqueous solutions by filtering off the oligomer precipitates. © 2010 American Institute of Chemical Engineers Environ Prog, 2011

Dynamics of polyelectrolyte complex formation and stability when a polycation is progressively added to a polyanion under physico-chemical conditions modeling blood

The formation of polyelectrolyte complexes is known to depend on many factors, especially pH, temperature, and ionic strength, as well as acid—base properties and mixing conditions. In an approach aimed at by-passing the complexity of blood, the formation and the stability of complexes between oppositely charged polymers were studied in salted media (0.15N NaCl and 0.13 M, pH 7.4 PBS) at room temperature. Different molar masses of poly(L-lysine) were reacted with polyanions with different chemical structures and charge densities, namely: poly(acrylic acid), poly(L-lysine citramide), poly(L-lysine citramide imide), and poly(malic acid). A stepwise protocol was used to investigate the fractionation phenomena reported previously. After each addition, the precipitate was separated and analyzed. The polyanion macromolecules were fractionated according to their structure; no significant fractionation was observed for the polycation. The NaCl concentration, required to destabilize the complexes in the isolated fractions, was found to depend on the polycation molar mass and to vary linearly with log(polyanion Mw). Based on these data, the possible fate of polycationic species, and of polycation-based polyelectrolytic complex, when injected into blood, are addressed.

Determination of optimum process parameters for peroxidase‐catalysed treatment of bisphenol A and application to the removal of bisphenol derivatives

Systematic investigations were carried out to determine the optimum process parameters such as the hydrogen peroxide (H2O2) concentration, concentration and molar mass of poly(ethylene glycol) (PEG) as an additive, pH value, temperature and enzyme dose for treatment of bisphenol A (BPA) with horseradish peroxidase (HRP). The HRP‐catalysed treatment of BPA was effectively enhanced by adding PEG, and BPA was completely converted into phenoxy radicals by HRP dose of 0.10 U/cm3. The optimum conditions for HRP‐catalysed treatment of BPA at 0.3 mM was determined to be 0.3 mM for H2O2 and 0.10 mg/cm3 for PEG with a molar mass of 1.0 × 104 in a pH 6.0 buffer at 30 °C. Different kinds of bisphenol derivatives were completely or effectively treated by HRP under the optimum conditions determined for treatment of BPA, although the HRP dose was further increased as necessary for some of them. The aggregation of water‐insoluble oligomers generated by the enzymatic radicalization and radical coupling reaction was enhanced by decreasing the pH values to 4.0 with HCl after the enzymatic treatment, and BPA and bisphenol derivatives were removed from aqueous solutions by filtering out the oligomer precipitates.

Effect of Polymer Molecular Weight on the Polymer/Surfactant Interaction

A thermodynamic analysis of the interaction between fourteen different molar mass poly(ethylene oxide)s (PEO) and sodium dodecyl sulfate (SDS) based on the measured surfactant-binding isotherms is given. The surfactant-binding isotherms were determined by the potentiometric method in the presence of 0.1 M inert electrolyte (NaBr). It was found that there is no PEO/SDS complex formation if M(PEO) < 1000. In the molecular weight range 1000 < M(PEO) < 8000, the critical aggregation concentration (cac) and the surfactant aggregation number are decreasing as the polymer molecular weight increases. The saturated bound surfactant amount is proportional to the number concentration of the polymer in this molecular weight range. If M(PEO) exceeds approximately 8000, the cac does not depend on the polymer molar mass, and the saturated bound amount of the surfactant becomes proportional to the mass concentration of the polymer. It was also observed that independently of the polymer molecular weight the surfactant aggregation number increases as the equilibrium surfactant monomer concentration increases from the cac to the critical micellar concentration (cmc). Finally, it was demonstrated that only one polymer molecule is involved in the complex formation independently of the polymer molecular weight.

Solution properties of well-defined 2-(dimethylamino)ethyl methacrylate-based (co)polymers: A viscometric approach

Well-defined poly(2-(dimethylamino)ethyl methacrylate)-based (co)polymers with various molar masses were synthesized by atom transfer radical polymerization (ATRP) using CuBr ligated with 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) as catalyst, and ethyl 2-bromoisobutyrate (EBiB) or α-methyl, ω-(2-bromoisobutyrate) poly(ethylene glycol) (mPEG x -BiB) as (macro)initiator. The solution properties of these (co)polymers were investigated by viscometry either in pure water or in concentrated buffer solutions. It comes out that reduced viscosity in pure water is strongly affected by the molar mass of poly(2-(dimethylamino)ethyl methacrylate) block but also by the quaternization degree of tertiary amino groups. In fact, a polyelectrolyte effect can only be detected when the charge density per macromolecule reaches a critical value either in terms of molar mass or quaternization degree. Fitting of viscometry data according to either Huggins or Fuoss and Fedors equation also allows calculating the intrinsic viscosity and approaching the overlap concentration.

Rapid Ring‐Opening Polymerization of D,L‐Lactide by Microwaves

AbstractSummary: Poly(D,L‐lactide) with a molar mass of 105 g · mol−1 and a yield over 90% was produced in 10 min by the ring‐opening polymerization of D,L‐lactide under microwave irradiation with forward power of 255 W. A degradation of the poly(D,L‐lactide) was also induced by microwaves with a power level over 340 W. The molar mass of poly(D,L‐lactide) was dependent upon the competition between the polymerization of D,L‐lactide and the degradation of the resulting polymer.Profiles of molar mass versus microwave irradiation time (1.8 g DLLA, 0.1% Sn(Oct)2).magnified imageProfiles of molar mass versus microwave irradiation time (1.8 g DLLA, 0.1% Sn(Oct)2).

Influence of chain length and temperature on UV-Vis absorption and degradation behavior of poly(diethyl dipropargylmalonate) with an alternating cis-trans-1,2-(cyclopent-1-enylene)vinylene structure

Cyclopolymerization of diethyl dipropargylmalonate (DEDPM) with Mo(N-2,6-i-Pr2-C6H3) (CHCMe2Ph)(OC(CH3)3)2 in the presence of quinuclidine yields poly(DEDPM) with an alternating cis-trans-1,2-(cyclopent-1-enylene)vinylene structure. Poly(DEDPM) n with different degrees of polymerization (n = 5–90) and PDI < 1.4 was prepared. A linear plot of number of monomers (N) added versus molecular weight as determined by light scattering (data were collected at λ = 690 nm) suggests that the cyclopolymerization of DEDPM proceeds in a living manner. A degree of polymerization (DP)-dependent UV-Vis absorption is found. At 25°C, the absorption maximum λmax for poly(DEDPM) n for n ≥ 50 is 591 nm. Thus, a maximum effective conjugation length N eff of 52 can be calculated. Increasing chain length results in a highly resolved fine structure in the UV-Vis spectrum with absorption maxima at 550 and 590 nm and a shoulder at around 513 nm for poly(DEDPM)70. In the solid state, absorption maxima were in the range of 478-574 nm for poly(DEDPM)5–90. Poly(DEDPM)10 and poly(DEPM)90 showed glass transition temperatures of 25.8 and 26.5°C, respectively. The measurement of λmax of poly(DEDPM)50 solutions in chloroform within a temperature range of 30°C reveals a reversible thermoresponsive behavior with changes in λmax of 8 nm. Poly(DEDPM) is stable under air over months in the solid state, as well as in solution using non-acidic solvents (e.g. CH2Cl2). In contrast, values for λmax for poly(DEDPM) solutions in CHCl3 decrease, if the solutions are exposed to air and light, yet remain constant in the absence of light and air. Changes in molar mass of poly(DEDPM) solutions in CHCl3 and CH2Cl2 were investigated by SEC measurements using light scattering detection and correlated with their time-dependent UV-Vis absorption behavior. Finally, poly(DEDPM)10–90 is thermally stable up to 185°C under a helium atmosphere.

Effect of Co- and Non-Copolymerizable Lewis Bases in Propylene Polymerization with EtInd2ZrCl2/MAO

This paper reports the effect of co- and non-copolymerizable Lewis bases in propylene polymerization with the soluble system EtInd2ZrCl2/MAO. With non-copolymerizable Lewis bases, the activity and the molar mass of poly(propylene) are diminished. This result is unusual because there is agreement about the cationic nature of the active site in Zirconocene/MAO systems and the effect of a Lewis base must be to decrease the termination constant versus the propagation constant, considering the diminished electrophilicity of Zr. In the case of copolymerizable Lewis bases, the negative effect on activity is higher. An explanation of the data is given, with a new model of Lewis bases/cationic Zr interaction, taking account of recent reports about the structure of active sites.

Molar mass of poly (ethylene terephthalate) (PET) during ultimate uniaxial drawing

The changes of the average molar mass Mw, Mn, Mz, and molar mass distributions during multistep uniaxial drawing of poly(ethylene terephthalate) (PET) to achieve ultimate mechanical properties have been studied in detail by means of size exclusion chromatography (SEC) with triple detection: concentration, viscosimetry, and light scattering, using HFIP as solvent. An increase in molar mass of PET due to post-polycondensation and/or transesterification during drawing at a high temperature of 160 to 230°C was found. Moreover, drawing leads to crystallization and large orientation in the amorphous phase, which results in lower molecular mobility and prevents a further growth in chain length. Crazing under extreme drawing conditions occurs and affects a decrease in molar mass.

Pervaporation separation of aqueous alcohol solution through the membrane ofo-trimethylsilylphenylacetylene initiated by a tungsten carbene complex

A poly(o-trimethylsilylphenylacetylene) [poly(o-TMSPA)] initiated by a tungsten carbene complex was investigated under various conditions. The molar mass of poly(o-TMSPA) increases with increasing the polymerization temperature and decreasing the initiator concentration. The X-ray diffraction measurements show that poly(o-TMSPA) has an amorphous structure. The water molecules preferentially permeate through the poly(o-TMSPA) membranes. The effects of feed compositions, degree of swelling, and the molecular size of alcohols on the pervaporation performances were investigated. The separation factor and the permeation rate increase with increasing ethanol concentration in the feed. The diffusivity contributes to a major part to selective transport. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 647–654, 1999