Poly(N-acryloyl-l-prolyl morpholine): a g.p.c. packing exhibiting novel temperature dependence in solute distribution coefficients

The synthesis of poly(N-acryloyl-l-prolyl morpholine), a new bead packing for the g.p.c. of small molecules, is described. Characteristic g.p.c. behaviour and high column efficiencies were observed in water and benzyl alcohol. Novel, reversible temperature variations in solute Wheaton and Bauman distribution coefficients were observed. This effect, which is most marked in water, is caused by thermo-reversible changes in network pore size distribution in the bead packing.     

Determination of sequence length distribution in SBR by ozonolysis-g.p.c. method

Sequence distribution of styrene-butadiene copolymer (SBR) was investigated by ozonolysis-g.p.c. All the double bonds of butadiene units in SBR were cleaved by ozonolysis in methylene chloride at ?30°C, followed by reduction degradation to alcohol with lithium aluminium hydride. The g.p.c. of the ozonolysis products observed with a u.v.-detector showed the peaks corresponding to styrene sequences and styrene-1,2 sequences. Hot- and cold-emulsion SBR samples contained short sequences consisting of 1 to 4 styrene units and 1,2 styrene units respectively. The average sequence length of cold-emulsion SBR was slightly longer than that of hot-emulsion SBR. A partial block SBR prepared by solution polymerization contained short styrene sequences of 1 to 5 units and long sequences having a broad distribution of $\text{M}{}_{\mathrm{w}}\text{M}{}_{\mathrm{n}}\text{= 1.6}$ with the maximum around 35 units. The styrene sequences containing the 1,2 unit was scarcely observed in this sample.     

Syntheses and conformational studies of poly(γ-N-alkyl-l-α,γ-diaminobutyric acids) and their carbobenzoxy derivatives

Three types of high molecular weight $\text{poly}\text{(γ-N-}\text{methyl}\text{, γ-N-}\text{carbobenzoxy-}\text{l}\text{-α, γ-}\text{diaminobutyric acid}\text{)}$, $\text{poly}\text{(γ-N-}\text{ethyl}\text{, γ-N-}\text{carbobenzoxy-}\text{l}\text{-α, γ-}\text{diaminobutyric acid}\text{)}$, and $\text{poly}\text{(γ-N-}\text{benzyl}\text{, γ-N-}\text{carbobenzoxy-}\text{l}\text{-α, γ-}\text{diaminobutyric acid}\text{)}$ were synthesized by the N-carboxyanhydride method. The helix-coil transition of these $\text{poly}\text{(γ-N-}\text{alkyl}\text{, γ-N-}\text{carbobenzoxy-}\text{l}\text{-α, γ-}\text{diaminobutyric acids}\text{)}$ in chloroform-dichloroacetic acid was followed by optical rotation measurements. The introduction of a methyl, an ethyl, or a benzyl group to the side chain of the carbobenzoxylated derivative of poly(l-α, γ-diaminobutyric acid) appeared to weaken the helical conformation at 25°C and altered the direction of the temperature induced helix-coil transition from a ‘normal’ to an ‘inverse’. For water-soluble $\text{poly}\text{(γ-N-}\text{alkyl-}\text{l}\text{-α, γ-}\text{diaminobutyric acids}\text{)}$, the coil-to-helix transition was little observed even when the polypeptides were uncharged at pH 12. At sufficiently high methanol concentration, however, the polypeptides underwent a complete transition from the random coil to the α-helical conformation even at pH 3.     

Comparison of molecular weight distribution models for polymers characterized by g.p.c.

A semi-empirical model which employs polynomials based on general free radical polymerization kinetics, is developed to describe the molecular weight distribution data as well as to evaluate the average molecular weights of a variety of commercial thermoplastics including polystyrene, poly(methyl methacrylate) and low density polyethylene. These novel expressions are equally applicable to a natural rubber sample with a bimodal distribution. Least-squares methods for the classical Schulz and Flory distribution functions are introduced to handle the g.p.c. data of the above polymers. Comparison of the results collected from various analyses indicates clearly that the polynomial model is the most versatile one in the sense that it can be utilized to smooth out satisfactorily the molecular weight distribution data of many polymers. In general, the Wesslau distribution function is particularly good for the highly branched polyolefin and the Schulz model is fairly effective for the addition polymers of moderately sharp molecular weight distribution, presumably with $\text{M}\text{?}{}_{\mathrm{<mtext>w</mtext>}}\text{M}\text{?}{}_{\mathrm{<mtext>n</mtext>}}\text{=3.0}$. However, the Flory and Tung distributions are found to be rather inferior in the present studies. On the basis of the current findings, a new procedure is suggested to facilitate the computations of the true average molecular weights from g.p.c. data directly.     

Studies of cyclic and linear poly(dimethyl siloxanes): 2. Preparative gel permeation chromatography

A preparative gel permeation chromatographic (g.p.c.) instrument has been constructed and used to separate broad fractions of cyclic poly(dimethyl siloxanes) into sharp fractions with heterogeneity indices $\text{M}\text{?}{}_{\mathrm{w}}\text{M}\text{?}{}_{\mathrm{n}}\text{= 1.05 ± 0.02}$. The number-average molecular weights $\text{M}\text{?}{}_{\mathrm{n}}$ of the cyclic polymer fractions obtained were as high as 50 000, corresponding to number-average numbers of skeletal bonds $\text{n}\text{?}{}_{\mathrm{n}}$ up to 1300. The concentrations of linear poly(dimethyl siloxanes) in all but the highest molecular weight cyclic polymer fractions prepared are believed to be negligible. The preparative g.p.c. instrument was also used to obtain some sharp fractions of linear poly(dimethyl siloxanes).     

G.p.c. and viscometric investigation on grafting of styrene-co-acrylonitrile polymer to ethylene propylene elastomer

Ethylene-co-propylene polymer (EPM) has been grafted by styrene-acrylonitrile (SAN). The grafting and molecular parameters of the graft polymers (EPM-g-SAN) have been investigated by means of viscometry and g.p.c. measurements. Viscometric molecular weight ($\text{M}\text{?}{}_{\mathrm{v.g}}$) parameters of the elastomeric backbone of the graft polymers and distribution of SAN content in relation to grafting conditions have been determined. Viscometric measurements in solvent mixtures have been made on EPM-g-SAN to study the functions of the SAN/EPM ratio and the molecular weight of grafted SAN. Viscometric behaviour is dependent on each of these factors.     

Synthesis of aminotelechelic polymers with the redox system TiCl3NH2OH in hydrochloric aqueous phase: 2. Polymerization of methylmethacrylate. Relation functionality/molecular weight/yield

Aminotelechelic poly(methylmethacrylates) of which number average molecular weight $\text{M}\text{?}{}_{\mathrm{n}}$ is less than 7 × 10³ are synthesized with the redox system $\text{TiCl}{}_3\text{NH}{}_2\text{OH}$ in hydrochloric aqueous phase. Functionality, molecular weight and yield are discussed on the basis of initiation, propagation and termination reactions. These considerations justify the influence of various factors such as the addition time of the TiCl₃ solution, the molar ration $\text{MMA}\text{TiCl}{}_3$ and the nature of the reducing ions. The evolution of molecular weights determined by g.p.c. confirms the interpretation of the results.     

In situ laser raman spectroscopy of the sulfiding of Moγ-Al2O3 catalysts

Raman spectra of sulfided $\text{Mo}\text{γ-}\text{Al}{}_2\text{O}{}_3$ catalysts were obtained using in situ techniques for two sulfiding methods. For samples sulfided by 10% $\text{H}{}_2\text{S}\text{H}{}_2$ at 400 °C, MoS₂ structures were observed. A stepwise sulfiding using 10% $\text{H}{}_2\text{S}\text{H}{}_2$, with spectra recorded at 150, 250, and 350 °C, resulted in observation of molybdenum oxysulfide, reduced molybdate, and surface “MoS₂” phases. Reexposure of these samples to air led to radical modification of the oxysulfide structures as well as transformation of some sulfide phases. A model incorporating terminal and bridging MoS bonding and anion vacancies is proposed. This model is based on the conversion of isolated and aggregated molybdate and MoO₃ species to oxysulfide and reduced molybdenum phases. Conversion of reduced molybdenum phases to sulfides is observed to be slow.     

Characterization and conformation of aromatic polyamides: poly(1,4-phenylene terephthalamide) and poly(p-benzamide) in sulphuric acid

The dilute solution properties of two aromatic polyamides, poly(1,4-phenylene terephthalamide) (PPDT) and poly(p-benzamide) (PBA) in 96% sulphuric acid, have been investigated by measurements of the intrinsic viscosity, by light scattering and by gel permeation chromatography (g.p.c.). The Mark—Houwink relation for PPDT indicates that the conformation is intermediate between a coil and a rod-like particle. The conformations of both aromatic polyamides have been determined precisely by coupling g.p.c., light scattering and viscosity and it was found that PPDT and PBA in 96% sulphuric acid are not very rigid particles. The rigidity has been characterized in terms of a worm-like chain. The persistence lengths q which evaluate the rigidity of the chain are $\text{q = 175 ± 25}\text{A}\text{?}$ for PPDT and $\text{q = 500 ± 100}\text{A}\text{?}$ for PBA has the more rigid polymer chain.     

Conversion of bituminous coal in COH2O systems: 2. pH Dependence

Under $\text{CO}\text{H}{}_2\text{O}$ systems at initial pH values s> 12.6, an Illinois No. 6 coal, PSOC-26, was converted to a fully pyridine-soluble product, with benzene and hexane solubilities of 50% and 18%, respectively. The product gases were H₂ and CO₂. However, the expected $\text{H}{}_2\text{CO}{}_2$ ratio of 1.0 based on the water gas shift reaction was not observed, but the deficit in hydrogen was found in the increased hydrogen content of the coal product. 95% coal carbon recovery and good hydrogen balances were obtained, and the coal products were found to be very similar to those from conventional tetralin systems. The results suggest an efficient base-catalysed process, and that $\text{CO}\text{H}{}_2\text{O}$ systems are useful for coal studies.     

Configurational sequence lengths in polyacrylonitrile and poly(acrylonitrile-CO-haloalkyl acrylate/methacrylate)s determined by 13C n.m.r.

The tacticity and number average sequence length of like ($\text{n}\text{?}{}_{\mathrm{<mtext>o</mtext>}}$), meso ($\text{n}\text{?}{}_{\mathrm{<mtext>m</mtext>}}$) and racemic ($\text{n}\text{?}{}_{\mathrm{<mtext>r</mtext>}}$) acrylonitrile (AN) triad units in polyacrylonitrile (PAN) prepared in both water and water—acetone (2:1 v/v) media and AN-3-chloro, 2-hydroxypropyl acrylate/methacrylate, AN-2-bromoethyl methacrylate and AN-2-chloroethyl acrylate copolymers have been calculated using ¹³C n.m.r. spectra of the polymer solutions concerned at a field strength of 24.99 MHz. The spectra reveal that PAN prepared in water medium has a greater percentage (33.4%) of isotactic units than PAN prepared in water-acetone (2:1 v/v) medium (28.3%). The tacticity distribution of AN sequences in PAN and the copolymers is found to be random ($\text{n}\text{?}{}_{\mathrm{<mtext>m</mtext>}}\text{?}\text{n}\text{?}{}_{\mathrm{<mtext>r</mtext>}}\text{?2.0}$) and the number average sequence length of AN sequences in a copolymer containing 14.8 mole% of 3-chloro, 2-hydroxypropyl methacrylate was 15.2.     

Study of relationship between network structure of g.p.c. gels and molecular size of permeable substance

Attempts were made to correlate the average size of the network of crosslinked vinyl acetate-glycidyl methacrylate (GMA) copolymer to the maximum size of permeable molecules when the copolymers were used as g.p.c. packing materials. The root-mean-square of the end-to-end distance $\text{(}\text{r}\text{?}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ of the hydrodynamic radius $\text{(}\text{s}\text{?}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, which characterizes the maximum extent of the molecules, were calculated. Meanwhile, the average size of the copolymer network, r_c, was estimated from the average molar weight between crosslinkages, this being calculated from the equilibrium rubber elastic modulus, E_r, obtained by dynamic discoelastic measurements. It was found that the maximum size which can permeate the copolymer decreases as the content of GMA in the copolymer increases. From viscoelastic measurements, E_r was found to increase as the content of GMA in the copolymer increases. Further, linear relationships were obtained among r_c, $\text{(}\text{r}\text{?}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, and $\text{(}\text{s}\text{?}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ covering the wide range of the copolymer composition.     

Graft copolymers from azodicarboxylate-functional pre-polymers: 1. Synthesis of azodicarboxylate-functional polystyrene

A synthetic sequence is described for the preparation of polystyrenes in the molecular weight range ($\text{M}\text{?}{}_{\mathrm{<mtext>n</mtext>}}$) 3 × 10³ to 2 × 10⁴ having terminal azodicarboxylate functionality with one functional group per polymer chain. The polymer end groups are characterized spectroscopically at each step in the synthetic sequence. The concentration of azodicarboxylate groups on the polymers is determined spectro-scopically and compared with the $\text{M}\text{?}{}_{\mathrm{<mtext>n</mtext>}}$ of the polymers as calculated from initiator/monomer ratio or as measured by g.p.c. analysis.     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Structural investigation on column-chromatographed vacuum residues of various petroleum crudes by 13C nuclear magnetic resonance spectroscopy

Proton and carbon-13 nuclear magnetic resonance spectroscopy of various vacuum residues and their fractionated samples were carried out to investigate average molecular structures. The structural parameters derived from carbon distribution agreed with those derived from p.m.r. within experimental error. In the aliphatic region of the c.m.r. spectra, characteristic peaks assignable to $\text{(CH}{}_2\text{)}{}_{\mathrm{n}}\text{? n ≧ 6 (29.7}\text{ppm}\text{)}$ and CH₃CH₂CH₂CH₂ (14.1 ppm) etc. can be observed. The relative intensities of these peaks suggest that the methylene chain contained in vacuum residues is much longer ($\text{(CH}{}_2\text{)}{}_{\mathrm{n}}\text{? n ≧ 12}$) than has been considered previously. Using the information about the aliphatic region of the c.m.r. spectrum and the structural parameters, an average structural model was deduced.     

Polycondensation of N-acetyl-D-glucosamine and structure of poly (N-acetyl-D-glucosamine)

$\text{N-}\text{Acetyl-}\text{d}\text{-glucosamine}$ was polymerized by the action of phosphorus in dimethyl sulphoxide or poly(phosphoric acid ester) in dimethylformamide. The structure of the synthetic poly ($\text{N-}\text{acetyl-}\text{d}\text{-glucosamine}$) was determined by chemical methods. Polymers obtained from the phosphorus pentoxide/dimethyl sulphoxide system were found to contain predominantly α-1,4-glycosidic linkages, whereas polymers from the poly(phosphoric acid ester)/dimethylformamide system contained many β-1,6-linkages. These polymers showed different c.d. spectra and o.r.d. curves in the Cotton band of the amide chromophore, which was attributed to the difference in the position of glycosidic linkages. A definite correlation was found between the shape of the c.d. spectrum and the fraction of 1,4-glycosidic linkages estimated by the Morgan—Elson method. The observed trend was in agreement with the data for naturally existing glycosaminoglycanes. The spectroscopic data supported the conclusion of the structural analysis by chemical methods.     

Palladiumπ - complexes as catalysts for olefin polymerization

Polymerization of different types of olefins was investigated with a $\text{palladium}\text{π-}\text{allylic complex}$ as catalyst. Polymerization was possible only with those olefins which have a bicyclo structure. Compounds with two double bonds reacted as easily as mono-olefins. The effect of temperature on reaction rate was studied and an activation energy of 21.3 kcal/mol calculated for the polymerization reaction of bicyclohepta-2,5-diene.     

Measurements of anisotropic light scattering: application to the determination of the difference Hh−Hv for θ=π2

By improving the performance of a photogoniodiffusometer, a technique for the accurate determination of various light scattering components has been developed. An original adaptation of the method is the measurement of $\text{(H}{}_{\mathrm{h}}\text{?H}{}_{\mathrm{v}}\text{)}{}_{\mathrm{90°}}\text{(H}{}_{\mathrm{v}}\text{)}{}_{\mathrm{90°}}$, the value of which is dependent only on the scattering particles shape. A few examples are presented.     

Model calculations of the phase behaviour of rod-like particles in solution: Polydisperse systems having asymmetric distributions of rod-lengths

Model calculations have been made of the phase behaviour, and compositions of the phases in the biphasic range, for polydisperse rod-like particles in solution. The special cases of a most-probable distribution (m.p.d.), an empirically modified most-probable distribution and asymmetric Gaussian distributions are considered. It is shown that the presence of species of very low molecular length in the m.p.d. result in $\text{v}{}^{\mathrm{<mtext>o</mtext>}}{}_{\mathrm{?}}\text{7}$, the volume fraction of polymer for which the system becomes wholly-anisotropic, being close to unity and thus the biphasic range for the case of this distribution is far larger than that normally found experimentally. The empirically-modified m.p.d. gives a narrower biphasic range than that for the m.p.d. Calculations for the asymmetric Gaussian distribution make it clear that $\text{v}{}^{\mathrm{<mtext>o</mtext>}}{}_{\mathrm{?}}\text{7}$ is determined by the low molecular length species in the distribution whilst $\text{v}{}^{\mathrm{<mtext>o</mtext>}}{}_{\mathrm{?}}\text{1}$, the volume fraction of polymer at which the system goes from isotropic to biphasic, is determined by the high molecular length species of the distribution. It is suggested that these distributions and those considered earlier are unable to adequately explain the observed dielectric and viscosity behaviour of rod-like molecules in solution. It is necessary to introduce a small high molecular weight tail to a chosen distribution in order to obtain agreement betwee between the calculate and the observed behaviour.     

Thermal decomposition of a vinyl chloride/vinyl acetate copolymer

The thermal decomposition of an 85% vinyl $\text{chloride}\text{15\%}$ vinyl acetate copolymer and its different fractions obtained by precipitation was studied by the thermogravimetric scanning (t.g.s.) technique. Analyses of the t.g.s. thermograms revealed the existence of two major steps in the decomposition reaction. The first occurs between 180 and 380°C during which hydrogen chloride and hydrogen acetate are given off. In the second, which occurs between 420 and 480°C, degradation of the carbon chain takes place. Both the order of reaction and the activation energy were found to be dependent on the molecular weight of the copolymer and on the heating rate at which the experiments were carried out. Analyses of the samples carried out by gel permeation chromatography (g.p.c.) after each decomposition revealed that, besides the two steps mentioned above, yet another step, viz. crosslinking, may be taking place at 180°C or below where the weight loss of copolymer is too small to be detected by t.g.s. The process of crosslinking, however, may take place at other temperatures as well. A higher degree of crosslinking has been associated with a higher acetate content in the copolymer. A comparison of g.p.c. results with those obtained by nuclear magnetic resonance spectra showed that, out of the three steric configurations of the copolymer, syndiotactic sequences are least resistant to thermal treatment followed in order by heterotactic and isotactic sequences.