Intrinsic viscosity–number average molecular weight relationship for poly(1,4‐butylene adipate) diol

The relationship between number average molecular weight (M_n) and intrinsic viscosity ([η]) was studied for poly(1,4‐butylene adipate) diol (PBAD) in tetrahydrofuran, toluene, and ethyl acetate at 25°C. Thus, a series of PBAD samples were prepared by polymerization between 1,6‐adipic acid and 1,4‐butanediol. The values of M_n for the samples were determined by end‐group analysis as well as by ebulliometry, and the average difference of M_n between the two analysis ways was about 2.69%. The Mark–Houwink–Sakurada equations for PBAD were obtained to relate [η] with M_n in the range of 1900–10,000. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of high molecular weight poly(tert.butyl acrylate)

High molecular weight poly(tert. butyl acrylate) s have been synthesized anionically using a technique derived from that of Teyssié et al. It was established that under proper conditions the sites remained living, allowing proper control of the molecular weight and yielding samples with narrow molecular weight distributions.     

Intrinsic viscosity–molecular weight relationship for low molecular weight nylon 6

Samples of nylon 6 have been prepared by the hexamethylene diamine-initiated polymerization of ?-caprolactam at 220°C. Fractionation of these with m-cresol–diethyl ether at 26°C yielded 15 amino-terminated fractions of M?_n of 337–10,940 determined conductometrically. Below M?_n = 4,306 the Mark-Houwink parameters in m-cresol at 30°C are K = 3.0 × 10^?3 dl/g and v = 0.53 ± 0.02. Thereafter v exhibits a pronounced increase. The value of K is similar to the values of Kθ derived from Stockmayer-Fixman plots of published data in good solvents. The findings thus corroborate a current hypothesis that fractionated, low molecular weight polymers in good solvents tend to behave viscometrically, as if they were under θ conditions (i.e., K = K_θ and v = 0.50).     

Intrinsic viscosity–molecular weight relationship and hydrodynamic volume for pullulan

A numerical method for determination of Mark–Houwink–Sakurada (MHS) equation constants, a and K, was tested with success for two series of pullulan standard samples having narrow and broad molecular weight distributions (MWD) and taken into account their polydispersity. Different solvents, which were used to determine the intrinsic viscosities and the viscometric constants, a and K (published in the literature for pullulan), were compared. The various parameters affecting the constants are discussed. The procedure to determine the correct value of the hydrodynamic volume for pullulan was also described. This study resulted in the following MHS equations for narrow and broad MWD series of pullulan samples with M_w in the range of 5–1000 kDa: where q_MHS is the polydispersity correction factor and [η] is the intrinsic viscosity in dL g^?1. The plot of log K versus exponent a was linear and inversely related. This curve was used to estimate the constant K for pullulan with a known exponent a. Among various reported solvents, the diluted aqueous salt solutions have more advantages than other solvents. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4325–4332, 2006     

Viscosity–molecular weight relationship for aminopropyl‐terminated poly(dimethylsiloxane)

Aminopropyl‐terminated poly(dimethylsiloxane) (ATPS) with different molecular weights was prepared by base‐catalyzed equilibration of octamethylcyclotetrasiloxane and 1,3‐bis(3‐aminopropyl)‐1,1,3,3‐tetramethyldisiloxane with different ratios. Their number‐average molecular weights (M_n) were determined by end–group analysis, and intrinsic viscosity ([η]) in toluene was measured with a Ubbelohde viscometer. A relationship between M_n and [η] was obtained for ATPS. For 1.0 × 10⁴ < M_n < 6.0 × 10⁴, it was in accord with [η]_{toluene,25°C} = 5.26 × 10^?2 M_n^0.587. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 975–978, 2001     

Dielectric relaxations in poly(methyl acrylate), poly(ethyl acrylate), and poly(butyl acrylate)

A comparative study is undertaken of the dielectric relaxation spectra of poly(methyl acrylate), poly(ethyl acrylate), and poly(butyl acrylate), taking into consideration the spectra of the corresponding polymers in the series of the polymethacrylates. The three polymers, PMA, PEA, and PBA, present an α relaxation zone clearly separated from the secondary relaxations. Its shape is not altered with temperature, and it is possible to construct a master curve. With increasing length of the side chain, its distribution of relaxation times broadens and the temperature of the maximum of the relaxation decreases. A β relaxation with decreasing intensity as the length of the side chain increases is clearly perceptible in PMA and PEA, but almost not perceptible at all in PBA. In PEA this relaxation appears split into two peaks. Computer simulation of restricted motions of the side chain discard an origin similar to that of the γ relaxation in PPA or PBA for the lowest temperature component of the relaxation, and suggests the conjunction of two rotation mechanisms in this relaxation for the polyacrylates. For the experimental temperatures of our tests a γ relaxation shows up only in PBA. Its apparent activation energy, higher than in related polymers of the polymethacrylate series, suggests that the tighter packing of monomeric units in polyacrylates leads to a significant increase in the intermolecular contribution to the potential energy barrier responsible for the relaxation.     

Preparation and properties of UV-curable poly(dimethylsiloxane) urethane acrylate. II. Property-structure/molecular weight relationships

A series of UV-curable polyurethane acrylate resins based on hydroxy-terminated polydimethylsiloxane (PDMS) soft segments with different molecular weights and various diisocyanate hard segments were synthesized. The products were obtained by employing direct-addition polymerization techniques in a nonsolvent system. The structures of the final products were elucidated by IR and ¹H-NMR. The fundamental and physical properties of this type of UV-curable material, the effects on properties by varying the molecular weight of PDMS or the type of diisocyanates, and the effect of using various reactive diluents were widely studied. This resin possessed good optical, electrical insulating, and adhesive properties. The mechanical strength of UV-cured films corresponds approximately to the ratio of hard segments within these material and the dielectric insulating properties correspond to the chain length of PDMS.     

Thermal stability of poly(methyl methacrylate-co-butyl acrylate) and poly(styrene-co-butyl acrylate) polymers

Thermal stability of poly(methyl methacrylate-co-butyl acrylate) and poly(styrene-co-butyl acrylate) modified with a small amount of acrylic acid and/or N-methylolacrylamide as a crosslinking agent was studied in this work. Programmed thermogravimetric analysis has been used to study the effect of copolymer composition on thermal stability, over a temperature range from 50 to 450°C, under a constant flow of nitrogen. Kinetic parameters of thermal degradation, activation energy, pre-exponential factor, and reaction order were obtained by using MacCallum-Tanner's approach. Kinetic data indicate that the thermal degradation of the investigated copolymer systems is the first order reaction, and that the increase of activation energy may be an indication of thermal stability changes in copolymer systems.     

GPC calibration for poly(methyl acrylate)

Summary Electrophylic vinyl reagents can be reacted with a protonated tertiary amine supported by a polymeric chain. We determined the mechanism of this addition in the case of vinyl methyl ketone and poly (4 vinyl pyridinium bromide). The first step is the addition of the vinyl compound on the tertiary amine, then protonation of the intermediate species occurs. The velocity constant at 268 K is 0.087 1. mole^–1. mn^–1 and the activation energy is 10 kcal.mole^–1.     

Measurement of molecular weight of poly(vinyl chloride)

Molecular weights of six bulk-process and five suspension-process PVC samples have been measured as part of a study aimed at developing a technique for gel permeation-chromatographic analysis of this polymer in tetrahydrofuran at room temperature. Osmometric M?_n values measured in cyclohexanone appear to be valid; the results are insensitive to thermal history or ultrasonic irradiation of the solution. Corresponding measurements in tetrahydrofuran changed with measurement temperature and indicated the presence of stable supermolecular PVC aggregates in this solvent. Such aggregates can be dispersed by ultrasonic treatment of the solution for brief periods. Simultaneous degradation of PVC molecules appears to be prevented by addition of small concentrations of nonionic surfactant to the tetrahydrofuran solutions. Treated solutions are suitable for GPC analyses at ambient temperatures. The results of osmometry, light scattering, and GPC agreed well.     

The depolymerization of low molecular weight poly(chloroacetaldehydes)

Stability of low molecular weight (D.P. < 300) polychloral has been found to be a function of the amine used as the polymerization initiator. The polymer produced with diethylamine unzips much more rapidly than that made with triethylamine. This investigation also showed that ester endcaps provide little protection from amine-induced depolymerization. The amine-initiated copolymer of chloral and dichloroacetaldehyde behaves anomalously in that it is unstable in the presence of normally inert organic solvents. Mechanisms are proposed to account for these observations.     

Synthesis,spinning, and properties of very high molecular weight poly(acrylonitrile-co-methyl acrylate) for high performance precursors for carbon fiber

In this paper, synthesis of very high molecular weight (VHMW) polyacrylonitrile-co-methyl acrylate (PAN-co-MA) polymers with weight average molecular weights of at least 1.7 million g/mole were repeatedly achieved on a laboratory scale using emulsion polymerization. The development of a hybrid dry-jet gel solution spinning technique for the VHMW PAN-co-MA enabled continuous spinning of 100 filament count tows, 100s of meters in length. Single filaments were analyzed and tested for tensile performance. Experimentally, the hybrid spinning method coupled with VHMW polymers produced precursor fibers with excellent tensile properties, averaging 954 MPa in strength and 15.9 GPa in elastic modulus (N = 296), with small filament diameters (5 μm). Results indicate a strong correlation between decreasing filament diameter, facilitated by high molecular weight polymer, and exponentially increasing tensile properties, using a hybrid dry-jet gel spinning process.     

Nucleophilic substitution reaction of ethanolamine onto poly(phenyl acrylate) and substituted poly(phenyl acrylate)s

The nucleophilic substitution reaction of differently substituted phenoxy groups with ethanolamine in various poly(phenyl acrylate)s was investigated in dioxane at 60, 80, and 100°C. The conversion, as determined from IR- and ¹H-NMR spectroscopy and elemental analysis, depends on the temperature and the kind of substituents at the phenyl ring.     

Poly(lauryl acrylate) and poly(stearyl acrylate) grafted multiwalled carbon nanotubes for polypropylene composites

Two new polymer grafts on an industrial grade multiwalled carbon nanotube (MWCNT) were prepared through a non-oxidative pathway employing controlled free radical polymerization for surface initiated polymer grafting. After photochemical introduction of an ATRP initiator onto the MWCNT, polymerizations of lauryl or stearyl acrylate were performed, resulting in two novel polymer modifications on the MWCNT (poly(lauryl acrylate) or poly(stearyl acrylate)). The method was found to give time dependent loading of polymers as a function of time (up to 38 wt% for both acrylates), and showed a plateau in loading after 12 h of polymerization. The modified nanomaterials were melt mixed into polypropylene composites with very low filler loading (0.3 wt%), whereafter both the thermal and electrical properties were investigated by DSC and dielectric resonance spectroscopy. The electrical properties were found to be substantially improved, where poly(lauryl acrylate) was found to be the superior surface modification, resulting in a conductive composite.     

Effect of molecular weight on crystallization isotherms of high molecular weight poly(ethylene oxide) fractions

Dilatometric crystallization isotherms have been determined for a set of poly(ethylene oxide) fractions ranging in molecular weight from 2 × 10⁴ to 1.6 × 10⁶. For a given fraction the isotherms obtained for different crystallization temperatures can be superimposed over most of the crystallization. For a given crystallization temperature the degree of crystallinity obtained in the primary stage of the crystallization varies greatly with molecular weight, and superimposition of the isotherms is not possible. Secondary crystallization processes are pronounced when the molecular weight ($\text{M}\text{?}{}_{\mathrm{v}}$) exceeds 10⁵.     

Crosslinked poly(sodium acrylate) hydrogels

Summary Samples of poly(acry1ic acid) (PAA) neutralized to varying degrees with sodium hydroxide were subjected to -irradiation to yield insoluble crosslinked polyacrylate hydrogels. The efficiency of crosslinking was found to be dependent on the degree of neutralization of the sample and the concentration of the irradiated polymer solution. The extent of water uptake of the gel was shown to be related to the degree of neutralization by titration of acid groups within the gel subsequent to cross-linking. Lightly crosslinked gels exhibited a maximum degree of swelling at a particular neutralization level. This was ascribed to a maximum in the long-range forces exerted cooperatively by the polymeric charges. The presence of simple electrolyte ions reduces swelling by screening these forces.     

A simple viscometric test for number average and weight average molecular weight of 12.6% N pyro nitrocellulose

In the poor solvent acetone/ethanol the viscosity of a 3% solution of 12.6% N pyro nitrocellulose is found to be related to the geometric mean of the number average and weight average molecular weights. The fractional increase in the viscosity of such a solution on the addition of lead ß-resorcylate is a function only of number average molecular weight. Once calibration has been made against osmotic pressure measurements and intrinsic viscosity, both number and weight average may be measured rapidly with an accuracy which is no less than that of the osmotic pressure and intrinsic viscosity measurements themselves.     

On the molecular weight determination of a poly(aryl-ether-ether-ketone) (PEEK)

Attempts have been made to determine the weight average molecular weight ($\text{M}\text{?}{}_{\mathrm{<mtext>W</mtext>}}$), the radius of gyration ($\text{R}\text{?}{}_{\mathrm{<mtext>G</mtext>}}$) and the second virial coefficient (A₂) of five samples of poly(ether-ether-ketone) (PEEK) by light scattering (LS) in concentrated sulphuric acid. Account has been taken of the sulphonation of the polymer. Correlations between LS-molecular weights, melt viscosities and intrinsic viscosities in sulphuric acid or in a $\text{50}\text{50}$ phenol-trichlorobenzene mixture have been established. Gel permeation chromatography (g.p.c.) analyses at 115°C have been performed in this latter solvent and two calibration methods were compared.     

High molecular weight poly( -lactide) and poly(ethylene oxide) blends: thermal characterization and physical properties

The miscibility of high molecular weight poly( -lactide) PLLA with high molecular weight poly(ethylene oxide) PEO was studied by differential scanning calorimetry. All blends containing up to 50 weight% PEO showed single glass transition temperatures. The PLLA and PEO melting temperatures were found to decrease on blending, the equilibrium melting points of PLLA in these blends decreased with increasing PEO fractions. These results suggest the miscibility of PLLA and PEO in the amorphous phase. Mechanical properties of blends with up to 20 weight% PEO were also studied. Changes in mechanical properties were small in blends with less than 10 weight% PEO. At higher PEO concentrations the materials became very flexible, an elongation at break of more than 500% was observed for a blend with 20 weight% PEO. Hydrolytic degradation up to 30 days of the blends showed only a small variation in tensile strength at PEO concentrations less than 15 weight%. As a result of the increased hydrophilicity, however, the blends swelled. Mass loss upon degradation was attributed to partial dissolution of the PEO fraction and to an increased rate of degradation of the PLLA fraction. Significant differences in degradation behaviour between PLLA/PEO blends and (PLLA/PEO/PLLA) triblock-copolymers were observed.