The oxidative polycondensation of 2-[(4-pyridilmethylene)-imino]phenol by molecular O2 in alkaline medium: Synthesis and characterization

Summary The polymer of 2-[(4-pyridilmethylene)-imino] phenol (2-PIP) has been formed from the oxidative polycondensation (OP) reaction by using molecular O₂ as the oxidant in an aqueous alkaline medium between 60–90 °C. The optimum reaction conditions and the main parameters of the process were determined. The yield of polymer was found as 50.1%. The structures of synthesized monomer and polymer were confirmed by FT-IR, UV-vis, ¹H-¹³C-NMR and elemental analysis. The characterization was made by TGA-DTA, size exclusion chromatography (SEC) and solubility tests. The ¹H-¹³C-NMR data shows that the polymerization proceeded with C-C and C-O-C coupling system of ortho and para positions and oxyphenylene according to –OH group of 2-PIP. The molecular weight distribution values of the product were determined from SEC measurement. The number-average molecular weight (M_n), weight-average molecular weight (M_w) and polydispersity index (PDI) values of poly-2-[(4-pyridilmethylene)-imino]phenol (poly-2-PIP) were found to be 11350, 12600 g.mol^-1 and 1.110, respectively. According to thermo gravimetric analysis (TGA), the carbon residues of 2-PIP and poly-2-PIP were found to be 18.17% and 45.10%, respectively, at 1000 °C.     

Polymerization of p-nitrobenzyl acrylate under microwave irradiation and their optical properties

p-Nitrobenzyl acrylate was polymerized under microwave irradiation initiated by benzoyl peroxide. The effect of the reaction conditions on the conversion, average molecular weights and the polydispersity index (M_w/M_n) were investigated. The polymers were characterized by IR, ¹H and ¹³C-NMR spectroscopies and molecular weights were analyzed with size exclusion chromatography (SEC). Optical properties in seven solvents were studied. The most outstanding characteristics of this monomer were slow kinetics of polymerization and low average molecular weight (M_w ~ 3000) as result of the chain transfer reaction to monomer, as it was demonstrated by experimental test and theoretical calculations. Solvatochromic effect of polymer solutions by changing the solvent polarity was quantitatively expressed by means of the linear solvation energy relationship using the empirical Kamlet-Taft solvents parameters set. The analyses demonstrated that the solute-solvent dipolar interactions were mainly responsible of the observed shift of ν_max and attributed to the para-nitrobenzyl group of the monomer, which enhanced the optical properties of the polymer.     

Synthesis,characterization, thermal stability,conductivity, and band gap of a new aromatic polyether containing an azomethine as a side

In this study, the oxidative polycondensation reaction conditions of 4‐[(4‐methylphenyl)iminomethyl]phenol (4‐MPIMP) were studied by using oxidants such as air O₂, H₂O₂, and NaOCl in an aqueous alkaline medium between 50 and 90°C. The structures of the synthesized monomer and polymer were confirmed by FTIR, UV–vis, ¹H–¹³C‐NMR, and elemental analysis. The characterization was made by TGA‐DTA, size exclusion chromatography (SEC), and solubility tests. At the optimum reaction conditions, the yield of poly‐4‐[(4‐methylphenyl)iminomethyl]phenol (P‐4‐MPIMP) was found to be 28% for air O₂ oxidant, 42% for H₂O₂ oxidant, and 62% for NaOCl oxidant. According to the SEC analysis, the number–average molecular weight (M_n), weight–average molecular weight (M_w), and polydispersity index values of P‐4‐MPIMP were found to be 4400 g mol^?1, 5100 g mol^?1, and 1.159, using H₂O₂, and 4650 g mol^?1, 5200 g mol^?1, and 1.118, using air O₂, and 5100 g mol^?1, 5900 g mol^?1, and 1.157, using NaOCl, respectively. According to TG analysis, the weight losses of 4‐MPIMP and P‐4‐MPIMP were found to be 85.37% and 72.19% at 1000°C, respectively. P‐4‐MPIMP showed higher stability against thermal decomposition. Also, electrical conductivity of the P‐4‐MPIMP was measured, showing that the polymer is a typical semiconductor. The highest occupied molecular orbital and the lowest unoccupied molecular orbital energy levels and electrochemical energy gaps (E) of 4‐MPIMP and P‐4‐MPIMP were found to be ?5.76, ?5.19; ?3.00, ?3.24; 2.76 and 1.95 eV, respectively. According to UV–vis measurements, optical band gaps (E_g) of 4‐MPIMP and P‐4‐MPIMP were found to be 3.34 and 2.82 eV, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis of π-Conjugated Ferrocene-Anthraquinone Alternating Polymers and their Protonation Reactions

The ethynylene-bridged ferrocene-anthraquinone system exhibits unique protonation-induced electron transfer reactions to form multi-dentate valence tautomerization states. In this study, we newly synthesized ethynylene-bridged ferrocene-anthraquinone alternating oligomers by a reaction of 1,1′-bis(trimethylstannylethynyl)ferrocene with 1,8-dibromoanthraquinone in the presence of a Pd(0) catalyst. An insoluble 1:1-donor/acceptor polymer, (1,1′-Fc-1,8-Aq) _n , was obtained and characterized by IR and UV-vis spectra and elemental analysis. The molecular weight of the soluble portion of the oligomers was M _w = 2.6 × 10³ (M _w/M _n = 1.4). A cyclic dimer, cyclic -(FcAq) ₂ , was also obtained and characterized by the 2D-NMR spectra. The behavior of the insoluble polymer (1,1′-Fc-1,8-Aq) _n upon the addition of an organic acid such as CF₃SO₃H was examined and compared with that of the monomer exposed to the same conditions. The addition of CF₃SO₃H to the insoluble polymer rendered soluble in organic solvent, and the changes in the UV-vis-NIR and IR absorption spectra reflected the structural changes to the protonated form with valence tautomers; this reaction was similar to the reactions with 1-ferrocenylethynylanthraquinone (1-FcAq) and 1,8-bis(ferrocenylethynyl)anthraquinone (1,8-Fc ₂ Aq). This paper is dedicated to Professor Ian Manners and his scientific accomplishments.     

Preparation of Polymers Containing Metal–Metal Bonds along the Backbone Using Click Chemistry

The [(η⁵-C₅H₄(CH₂)₃OC(O)(CH₂)₂C≡CH)Mo(CO)₃]₂ complex (1) was synthesized and used to explore the feasibility of using the Huisgen cycloaddition reaction (a click reaction) to incorporate molecules with metal–metal bonds into polymer backbones. In a model reaction, coupling of 1 with benzyl azide was observed in 24 h using Cp*Ru(PPh₃)₂Cl as a catalyst. In contrast, the reaction of 1 with benzyl azide using a CuBr/ligand catalyst (where the ligand is either PMDETA or bipyridine), resulted in disproportionation of the Mo–Mo unit in 1. Complex 1 was also coupled with telechelic azide-terminated polystyrene oligomers. With either the CuBr/PMDETA or CuBr/bipyridine catalyst, disproportionation of the Mo–Mo bonded unit occurred before complete coupling was observed. The reaction was also slow when the Cp*Ru(PPh₃)₂Cl catalyst was used; however, no disproportionation products were observed and a high molecular weight polymer (M _n = 120,000 g/mol) was produced. The Cp*Ru(PPh₃)₂Cl catalyst was also used to couple 1 with azide-terminated poly(ethylene glycol). After 15 h, this reaction produced a polymer with M _n = 73,000 g mol⁻¹. It is concluded that, although somewhat slow, click chemistry using the Cp*Ru(PPh₃)₂Cl catalyst is an excellent method for synthesizing high molecular weight polymers with metal–metal bonds along the backbone.     

Polypentamethylnadimides obtained by Diels-Alder reaction

The reactions between benzylbromide or α,α′-dibromo-meta-xylene (DBMX) and sodium 1,2,3,4,5-pentamethylcycopenta-1,3-dienide (CpMe₅^?, Na^⊕) give only the expected pentamathylcyclopentadiene derivatives with a good yields. These products lead to endo isomer adducts via a Diels-Alder reaction with maleimide.New low molecular weight polypentamethylnadimides were obtained in this way from the Diels-Alder polymerization of bispentamethylcyclopentadiene monomers and commercial or synthetic bismaleimides. The polyadducts were characterised by size exclusion chromatography (SEC), matrix assisted laser desorption ionization-time of flight (MALDI-TOF), nuclear magnetic resonance (NMR) and thermogravimetric analyses (TGA).The low molecular weight was attributed to methyl steric hindrance. For the lowest molecular weight products, two different endcapped oligomers were observed.     

PEO-functionalized polystyrene as polymeric support in metallocene catalysed olefin polymerisation

Summary A new catalyst system based on easily accessible cross-linked (by Diels-Alder reaction) polymeric supports, functionalized with nucleophilic polyethyleneoxide-monomethylether (PEO-M) is presented. The metallocene-MAO complex is noncovalently bonded to the support, avoiding a complicated polymer analogous metallocene synthesis. The polymerisation of propene and ethene with Me₂Si(2MeBenzInd)₂ZrCl₂ as metallocene is performed using this support. The resulting polymers have high molecular weights and melting points and narrow molecular weight distribution. Polypropene is produced with 95% isotacticity similar to that from homogeneous catalysis. The productivities of up to 8600 for polypropene and 1300 for polyethene ( kg polymer / mol Zr h bar ) are comparably high. The product beads exhibit a good morphology, which can be explained by fragmentation processes of the support due to the reversibility of the network formation. Received: 21 February 2001/Revised version: 2 November 2001/ Accepted: 6 November 2001     

Synthesis,characterization, conductivity,band gap,and kinetic of thermal degradation of poly‐4‐[(2‐mercaptophenyl) imino methyl] phenol

The oxidative polycondensation reaction conditions of 4‐[(2‐mercaptophenyl) imino methyl] phenol (2‐MPIMP) were studied in an aqueous acidic medium between 40 and 90°C by using oxidants such as air, H₂O₂, and NaOCl. The structures of the synthesized monomer and polymer were confirmed by FTIR, ¹H NMR, ¹³C NMR, and elemental analysis. The characterization was made by TGA‐DTA, size exclusion chromatography (SEC) and solubility tests. At the optimum reaction conditions, the yield of poly‐4‐[(2‐mercaptophenyl) imino methyl]phenol (P‐2‐MPIMP) was found to be 92% for NaOCl oxidant, 84% for H₂O₂ oxidant 54% for air oxidant. According to the SEC analysis, the number‐average molecular weight (M_n), weight‐average molecular weight (M_w), and polydispersity index values of P‐2‐MPIMP were found to be 1700 g mol^?1, 1900 g mol^?1, and 1.118, using H₂O₂; 3100 g mol^?1, 3400 g mol^?1, and 1.097, using air; and 6750 g mol^?1, 6900 g mol^?1, and 1.022, using NaOCl, respectively. According to TG analysis, the weight losses of 2‐MPIMP and P‐2‐MPIMP were found to be 95.93% and 76.41% at 1000°C, respectively. P‐2‐MPIMP showed higher stability against thermal decomposition. Also, electrical conductivity of the P‐2‐MPIMP was measured, showing that the polymer is a typical semiconductor. The highest occupied molecular orbital, the lowest unoccupied molecular orbital, and the electrochemical energy gaps (E′_g) of 2‐MPIMP and P‐2‐MPIMP were found to be ?6.13, ?6.09; ?2.65, ?2.67; and 3.48, 3.42 eV, respectively. Kinetic and thermodynamic parameters of these compounds investigated by MacCallum‐Tanner and van Krevelen methods. The values of the apparent activation energies of thermal decomposition (E_a), the reaction order (n), pre‐exponential factor (A), the entropy change (ΔS*), enthalpy change (ΔH*), and free energy change (ΔG*) were calculated from the TGA curves of compounds. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A convenient route to high molecular weight highly isotactic polystyrene using Ziegler-Natta catalysts and ultrasound

Ziegler-Natta (TiCl₄/AlEt₃) catalysts and ultrasound were used to prepare highly isotactic polystyrene (ca. 99%) with a molecular weight of 4.7×10⁶ mol g⁻¹ and low molecular weight distribution (M_w/M_n=1.6) via a convenient method. Ultrasound was most effective if applied only during an initial stage in the polymerisation, most likely permitting dispersion of catalyst particles which were subsequently coated and separated by growing polymer chains. Yields could be improved by varying the amount of catalyst and reaction time.     

Organic-inorganic polymers: Synthesis and characterization of cyclophosphazene-substituted polyurethanes

The object of this work was to prepare organic inorganic oligomers or polymers from diisocyanates and hydroxylated cyclotriphosphazenes. The reaction of a dihydroxylated cyclotriphosphazene. (3.5-dihydroxyphenoxy)(pentaphenoxy) cyclotriphosphazene.3. obtained by the reaction of (3.5-dimethoxyphenoxy) (pentaphenoxy)cyclotriphosphazene with BBr₃ H₂O and two diisocyanates, toluen 2.4 (TDI)- and hexamethylene 1.6 (HDI)-diisocyanates, leads to the new cyclotriphosphazene-substituted polyurethanes,4 and5. The structures of both classes of compounds were investigated by³¹P.¹³C. and¹H NMR. infrared spectroscopy, mass spectrometry, and elemental analysis. The molecular weights of polymers were determined by SEC analysis. The thermal behavior of the new polyurethanes was investigated. The thermogravimetric analysis indicates that incorporation of cyclotriphosphazene moiety as a pendant group leads to increased thermal stability.     

Telechele als bausteine für neuartige polymere

The developments in the syntheses of α,ω-bifunctional oligomers (telechelics) are revued. Telechelic soft segments are synthesized by cationic, anionic and radical polymerization of vinyl and heterocyclic monomers. Telechelic PTHF obtained with CH₃CO⁺/Ac₂O stems from an equilibrating process and not from a transfer reaction. Telechelic polyisobutene is formed by the inifer technique of Kennedy. The use of lithium initiators with protected functional groups in butadien polymerization results in products with high 1.4-content. The group transfer polymerisation is specially suited to prepare telechelic PMMA of narrow molecular weight distribution. The “dead end” polymerisation is a necessary condition to obtain a functionality of two by radical polymerization. The synthesis of telechelic hard segments of the PPO and PPS type is described.     

Low-angle laser light scattering–aqueous size exclusion chromatography of polysaccharides: Molecular weight distribution and polymer branching determination

A low-angle laser light scattering detector (LALLS) used with size exclusion chromatography (SEC/LALLS) has been applied for the determination of molecular weight, molecular weight distribution (MWD), and degree of branching of polysaccharides in 0.5N NaOH aqueous solution. Data from both detectors [differential refractive index (DRI) and LALLS] are used to calculate the absolute molecular weight at each point in a sample chromatogram. The correct average molecular weight and MWD can be obtained without calibration methods used in conventional SEC. As a consequence of this technique, Mark—Houwink coefficients can be predicted from a single broad-distribution, homopolymer without recourse to time-consuming fractionation methods. Moreover, the hydrodynamic volume separation mechanism of SEC can be exploited with the SEC/LALLS method to gain information about polymer branching. In the studies described in this paper, SEC/LALLS has been employed to obtain data about the branching parameters g_v and g_M for samples of amylose, amylopectin, starch, and glycogen. For three homopolymers (amylose, amylopectin, and glycogen), branching frequency (as measured by chemical means), and the branching parameters (g_v and g_M) are inversely related. This trend is consistent with theoretical predictions. For starch, a nonhomogeneous branching distribution is observed as a function of molecular weight.     

Synthesis, Characterization, Conductivity, Band Gap, and Thermal Analysis of Poly-[(2-mercaptophenyl)iminomethyl]-2-naphthol and Its Polymer–Metal Complexes

Oxidative polycondensation reaction conditions of [(2-mercaptophenyl)iminomethyl]-2-naphthol (2-MPIM-2N) were studied using oxidants such as air and NaOCl in an aqueous alkaline medium between 40 °C and 90 °C. The structure of poly-[(2-mercaptophenyl)iminomethyl]-2-naphthol (P-2-MPIM-2N) was characterized by ¹H- ¹³C NMR, FT-IR, and UV–Vis spectroscopy, size exclusion chromatography (SEC), and elemental analysis. At optimum reaction conditions, the yield of P-2-MPIM-2N was found to be 78 and 82% for air and NaOCl oxidants, respectively. From SEC measurements, the number-average molecular weight (M _n ), weight-average molecular weight (M _w ) and polydispersity index (PDI) of P-2-MPIM-2N are 2900, 3500 g mol⁻¹ and 1.207; 2200, 2500 g mol⁻¹ and 1.136, for air and NaOCl oxidants, respectively. Polymer–metal complexes were synthesized by the reaction of P-2-MPIM-2N with Co²⁺, Cu²⁺, Zn²⁺, Pb²⁺ and Cd²⁺ ions. The highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), and electrochemical band gaps (E^￠_g E^{\prime}_{g} ) of 2-MPIM-2N and P-2-MPIM-2N were −5.97, −2.66 and 3.31 eV and −5.82, −2.68 and 3.14 eV, respectively. The conductivity of polymer and polymer–metal complexes were determined in the solid state. Conductivity measurements of doped and undoped Schiff base polymer and polymer–metal complexes were carried out at room temperature and atmospheric pressure by the four-point probe technique using an electrometer. The conductivities of the polymer and polymer–metal complexes increased when iodine was used as doping agent.     

Synthesis and characterization of low relative molecular weight trans‐1,4‐poly(isoprene)

Low relative molecular weight trans‐1,4‐polyisoprene oligomers were synthesized successfully by bulk precipitation and solution polymerization with supported titanium catalyst using hydrogen as relative molecular weight modifier. The effects of polymerization conditions on intrinsic viscosity ([η]), catalyst efficiency (CE) and structure of polymer were studied. Increasing the hydrogen pressure resulted in the decrease of [η] of the polymer. With the increasing of hydrogen pressure and reaction temperature, CE decreased but still maintained above 2500 g polymer/g Ti. The percentage composition of (trans‐1, 4‐unit) in the polymer was over 90% in all results. The crystallinity of polymer was about 50–60% with T_m being about 60°C. The relative molecular weight distribution index (MWD) was quite difference according to the polymerization method. While number average molecular weight (M_n) exceeded 860, polymer turned from viscous materials to fragile wax materials, and then to toughness materials at 1800. Dynamic property testing showed that the additional of this oligomer could increase the wet‐skid resistance of the rubber. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and optical properties of the [2.2]paracyclophane-containing π-conjugated polymer with a diacetylene unit

Summary Novel through-spaceπ-conjugated polymer based on poly(p-henyleneethynylene)/poly(p-phenylenebutadiynylene) hybrids containing a [2.2]paracyclophane unit in the main chain was synthesized by copper-catalyzed alkyne coupling reaction. The structure of the polymer was supported by ¹H NMR and IR spectra. The obtained polymer was soluble in common organic solvents such as THF, CH₂C1₂, CHC1₃ and toluene. The number-average of molecular weight of the polymer was estimated to be 63000 by GPC. The polymer emitted a bluish green light in solution and in the solid state. Received:24 September 2002/Revised version: 19 November 2002/Accepted: 19 November 2002 Correspondence to Yoshiki Chujo     

Effect of molecular weight distribution on polymer diffusion during film formation of two-component high-/low-molecular weight latex particles

We describe fluorescence resonance energy transfer (FRET) studies of film formation by a new type of two-component latex particles. These particles consist of a miscible blend of two components that have a similar composition but very different molecular weights. In our approach, we used sequential seeded emulsion polymerization to generate (in situ) a fraction of oligomer in poly(butyl acrylate-co-methyl methacrylate) P(BA-MMA) seed particles that contained a relatively high molecular weight (high-M) dye-labeled polymer. In this way we could systematically change the molecular weight distribution of polymer inside the particles. We varied the amount and the molecular weight of the oligomers. For latex films cast from these two-component particles, we studied the diffusion rate of the high molecular weight polymer by FRET. These measurements revealed that oligomers promoted diffusion rate during latex film formation (oligoplasticization). We analyzed our diffusion data in terms of the Fujita–Doolittle free-volume model and showed that higher molecular weight oligomers are less efficient as plasticizers. In separate experiments, oligomers with similar molecular weights as those in the two-component particles were introduced via latex blending. We compared oligoplasticization in latex blends films with that in the two-component particles films. Finally, we investigated the rheological behavior of the two-component polymers with compositions adjusted to have a common T_g (2 °C). The higher the molecular weight of the oligomer, the more that had to be added to achieve T_g = 2 °C. All of the oligomers were much shorter than the entanglement length and act as diluents of the entanglements in the high-M polymer. We found that incorporating larger amounts of oligomers with a higher molecular weight resulted in a more pronounced drop in polymer viscosity, associated with the decrease in the entanglement density.     

Synthesis and characterization of natural rubber-based telechelic oligomers via olefin metathesis

Metathesis degradation and functionalization of natural rubber (NR) were conducted with 1-hexene, 1-octene, 1-decene, 1-dodecene, trans-stilbene, and 4,4′-dibromo-trans-stilbene as chain transfer agents (CTAs) in presence of Grubbs 2nd generation catalyst to generate NR-based telechelic oligomers that had been a long-lasting challenge due to the structure and compositions of NR with various impurities. Orthogonal experiments were applied and the effects of the CTA type, CTA concentration, catalyst concentration, reaction time, and reaction temperature on the formation of telechelic oligomers were studied, indicating that the catalyst concentration was the major factor influencing the number average molecular weights (M_n) and polymer dispersity index (PDI) of telechelic oligomers. The structures of the oligomers were characterized using ¹H NMR, ¹³C NMR, and MALDI-TOF-MS, which confirmed the formation of the designed terminal groups. The results showed that well-defined telechelic oligomers with a M_n of a few thousand and a PDI around 1.6 were obtained, with potential applications in binder, lubricant and many other fields.     

The cationic oligomerization of p-aminostyrene 1. Trifluoroacetic acid-catalyzed polyaddition

Summary It was found that p-aminostyrene (PAS) was easily oligomerized by CF₃COOH (TFA) in CCl₄ to give a low molecular weight oligomer 4 including phenylene, ethylidene and secondary amine groups in the backbone, i.e., the isomer of poly-p-aminostyrene 5. The NMR and IR spectra of the product are quite different from those of polymer 5 produced by 2,2'-azobisisobutyronitrile (AIBN) in toluene. The dimer D and trimer T were separated from the reaction solution through the preparative GPC. The reaction seems to proceed stepwisely to give D in the initial stage and finally the near pentameric oligomer 4 at the end of the reaction. Received: 27 July 2000/Revised version: 8 September 2000/Accepted: 18 September 2000     

Cationic oligomerization of 1-hexene catalyzed by EtAlCl2–chloroacetic acid complexes

Lower oligomers (dimer to tetramer) of 1-hexene were obtained in high yield (65 wt %) with a new cationic complex catalyst, EtAlCl₂? CCl₃CO₂H, in n-hexane at 70°C, trimer being the major product. A strong oxo acid, CF₃SO₃H, yielded very similar products under the same conditions. Characteristics of the 1-hexene oligomerization by these two catalysts were the high selectivity for dimers to tetramers and the absence of cracking of the product. In contrast, EtAlCl₂ or AlCl₃ alone led to oligomers with a higher molecular weight (～10³) and a broad molecular weight distribution, the structure of which was very complicated because of extensive cracking of products. A series of EtAlCl₂? chloroacetic acid (CCl_nH₃–nCO₂H, n = 0–3) complexes were also examined as catalysts. The yield of dimer to tetramer increased with increasing acidity of the chloroacetic acids. The mechanism of the 1-hexene oligomerization with these complex catalysts was discussed on the basis of the structure of product oligomers.     

Calibration of size-exclusion chromatography columns with polydisperse polymer standards. II. Applications

New methods for calibrating SEC columns by means of polydisperse polymer samples with known M_n and M_w have been tested with computer-generated chromatograms and with experimental data of high-performance SEC. Calculations with the artificial chromatograms show that accurate calibration dependences can be recovered even when polymers with broad and/or bimodal molecular weight distributions are used as standards. Polystyrene calibration calculated by the proposed method from chromatograms of five polydisperse polystyrenes follows closely the curve obtained in a conventional manner from nine narrow polystyrene standards. The dependence log M vs. ν for PMMA determined from chromatograms of six PMMA samples with moderately broad molecular weight distributions agrees well with the curve obtained by shifting the dependence for polystyrene using the universal calibration concept. The new method is particularly useful when SEC columns are to be calibrated for dextrans in water, where only a few standards having a rather broad molecular weight distribution are available, and can considerably improve the accuracy of molecular weight determination by SEC.