Intermolecular Forces and Mechanical Behavior of High Polymers

1943 ◽  
Vol 16 (2) ◽  
pp. 268-279
Author(s):  
H. Mark
Keyword(s):  
Chemical Nature ◽  
Mechanical Performance ◽  
Structural Characteristics ◽  
Average Molecular Weight ◽  
Length Distribution ◽  
Intermolecular Forces ◽  
Chain Length Distribution ◽  
Chain Molecules ◽  
Acid Nitrile ◽  
High Polymers

Abstract In order to connect the mechanical properties of high polymers with their fundamental architecture, several structural characteristics must be considered. There is, first, the average molecular weight or the average polymerization degree of the substance, which varies between 20,000 and 1,000,000 or between 100 and 5000, respectively. There is the chain-length distribution curve, which describes the heterogeneity of the material, and is comparatively narrow in some cases and fairly wide in others. There is the chemical nature of the monomer, which can be a hydrocarbon, an alcohol, ester, ether, amine, acid, nitrile, etc., so that the polymer can have very different chemical characteristics. There are, finally, the intermolecular forces between the chain molecules, which are a consequence of the chemical nature of the monomer, and which, together with the flexibility of the chains, have a preponderant influence on mechanical performance.

scholarly journals The molecular-weight distribution of glycosaminoglycans

1973 ◽  
Vol 135 (4) ◽  
pp. 631-637 ◽  
Author(s):  
John J. Hopwood ◽  
H. Clem Robinson
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Chondroitin Sulphate ◽  
Average Molecular Weight ◽  
Length Distribution ◽  
Accurate Estimation ◽  
Distribution Data ◽  
Gel Chromatography ◽  
Chain Length Distribution

1. A rapid and sensitive method for the accurate estimation of the molecular-weight distribution of keratan sulphate and chondroitin sulphate isolated from adult bovine nasal septum and intervertebral disc is described. The method utilizes gel chromatography of reductively labelled glycosaminoglycan and end-group estimation of number-average molecular weight for each fraction across the peak of eluted glycosaminoglycan. 2. Chain-length distribution data obtained by this procedure are used to evaluate mechanisms of chondroitin sulphate biosynthesis.

THE DEGRADATION OF POLYSTYRENE: II. THE SYNTHESIS AND DEGRADATION OF POLYSTYRENE POSSESSING THE KUHN–SCHULZ CHAIN LENGTH DISTRIBUTION

1950 ◽  
Vol 28b (7) ◽  
pp. 416-428
Keyword(s):  
Molecular Weight ◽  
Benzoyl Peroxide ◽  
Chain Length ◽  
Average Molecular Weight ◽  
Length Distribution ◽  
Chain Scission ◽  
Limited Range ◽  
Number Average Molecular Weight ◽  
Chain Length Distribution ◽  
Synthesis And Degradation

By polymerizing styrene in emulsion it was possible to synthesize polystyrenes of known number average molecular weight, the chain length distributions of which corresponded closely to the Kuhn–Schulz relation Ny = N0py−1(1 − p)2. This enabled a relation between intrinsic viscosity and number average molecular weight to be established for polystyrenes with chain length distributions of this functional form. Assuming this form of chain length distribution to remain unaltered on degradation, it was possible to estimate the average number of scission points per structural unit from viscosimetric measurements. The extent of thermal scission of polystyrene after one week at 144 °C. was shown to be negligible while benzoyl peroxide caused appreciable chain scission at 80 °C. and 100 °C. The number of scission points estimated from viscosimetric measurements was directly proportional to the mass of benzoyl peroxide added to the system, and the scission appeared to be essentially random over the limited range investigated.

Network Chain Distribution and Strength of Vulcanizates

1969 ◽  
Vol 42 (3) ◽  
pp. 659-665 ◽  
Author(s):  
S. D. Gehman
Keyword(s):  
Physical Properties ◽  
Chain Length ◽  
Random Distribution ◽  
Length Distribution ◽  
Chain Scission ◽  
Point Of View ◽  
Average Chain Length ◽  
Chain Length Distribution ◽  
Network Chain ◽  
Chain Molecules

Abstract Physical characteristics of rubber network structures usually enumerated and discussed are network chain density, crosslink functionality, average chain length between crosslinks, entanglements which act somewhat like crosslinks, and free chain ends which are network defects. Chemical factors include structure of the chain molecules, type of crosslinks, whether monosulfide, disulfide or polysulfide, or direct carbon-to-carbon bonds. Side effects of vulcanization reactions such as chain scission or combination of minor quantities of chemical fragments from the vulcanizing system are also recognized. One might think that these variables would be adequate to account for physical properties of elastomers but explanations of strength aspects of vulcanizates are still unsatisfactory. Something is missing in these considerations, that is, the distribution of crosslinks along a main chain or the length sequences of monomer units in network chains. Usually a random distribution is implicitly assumed. If the distribution is always random and nothing can be done about it and it cannot be measured anyway, there may seem to be little point in writing about it. However, an ideally random distribution for all crosslinking systems and polymers seems very improbable. The importance of network chain length distribution for physical properties has been, of course, well recognized in theory. Bueche's calculations showed that viscoelastic resistance to deformation increased markedly with increased crosslink functionality, that is, as more chains are involved in the displacement of a crosslink. His molecular theory of tensile strength was based on the concept of short, overloaded network chains which snapped and transferred their loads to neighboring chains. An alternate point of view is that short chains are detrimental because they do not stress orient as well as longer chains.

Effect of Chain Length Distribution on the Tearing Energy of Silicone Elastomers

1987 ◽  
Vol 60 (1) ◽  
pp. 78-88 ◽  
Author(s):  
L. C. Yanyo ◽  
F. N. Kelley
Keyword(s):  
Average Molecular Weight ◽  
Length Distribution ◽  
Fracture Plane ◽  
Strength Increase ◽  
Experimental Conditions ◽  
Chain Length Distribution ◽  
Threshold Strength ◽  
Tearing Energy ◽  
Chain Lengths ◽  
Long Chains

Abstract The tearing energies of two endlinked PDMS networks, one a monomodal distribution of chain lengths and the other a bimodal mixture of very short and rather long chains, at the same average molecular weight between crosslinks, were compared. The bimodal network exhibited higher tearing strengths than the monomodal network under the same experimental conditions. At threshold conditions, the bimodal network tearing energy was 70% higher than the threshold strength of the monomodal network. A rederivation of the Lake and Thomas theory for the threshold tearing strength which includes a bimodal probability distribution of chain lengths is shown to predict the observed behavior. The strength increase of these bimodal networks is attributed to the presence of the long chains which increases the energy required for fracture while maintaining the same number of chains crossing the fracture plane as in the monomodal network of the same crosslink density, by including a large number of short chains.

High-polymer solutions

1952 ◽  
Vol 212 (1110) ◽  
pp. 339-361 ◽  
Keyword(s):  
Molecular Weight ◽  
Statistical Method ◽  
Osmotic Pressure ◽  
Chain Length ◽  
Natural Extension ◽  
Length Distribution ◽  
Published Data ◽  
Chain Length Distribution ◽  
Chain Molecules ◽  
Random Flight

In describing the configurations of a polymer molecule in terms of the ‘equivalent chain’ of N elements, each of length l , it has been usual to simplify the problem by assuming the equivalent chain to have position only and zero volume. The weights of the various configurations of such a ‘random flight’ chain are different from those of a real chain in which there exists an interaction potential between any pair of chain elements. These differences are particularly important in the theory of solutions of chain molecules, since they are responsible for the deviation of the osmotic pressure from van’t Hoff’s law. In this paper the average dimensions of a chain with interactions are calculated by a statistical method. For < s 2 >, the average square distance of the elements from the centre of gravity, the result is < s 2 > = ( Nl 2 /6) [1 - 0⋅857( β 1 / l 3 ) N -½ ], (i) where β 1 is the ‘excluded volume’ integral for free chain elements. For large N this reduces to the well-known result for a random flight chain. Similar results are obtained for other average dimensions. The possibility of checking (i) from experimental determinations of <s 2 > for chain molecules using the light-scattering technique is examined, and it is shown that a very accurate knowledge of the chain-length distribution in the fractions used will be required if the influence of the second term in (i) is to be detected in this way. A natural extension of the statistical method is used to calculate the pair distribution function F 2 ( X 12 ) governing the probability of occurrence of the centres of gravity of two chains in equal volume elements separated by the distance X 12 . This function is needed to calculate the second coefficient A 2 in the osmotic pressure expansion π = RT [ M -1 c + A 2 c 2 +...]. Here M is the molecular weight of the solute and c the concentration. For random flight chains F 2 is unity for all values of X 12 ; A 2 is zero and the osmotic pressure follows van’t Hoff’s law. Values of F 2 different from unity, and hence finite values of A 2 are only obtained if there are interactions between chain elements. The first approximation to F 2 is F 2 ( X 12 ) = exp {(9/2 π ) 3/2 ( β 1 / l 3 ) N ½ exp (-9 X 2 12 /2 Nl 2 )}. The theory predicts a rather complicated dependence of A 2 on z , the degree of polymerization and the log-log plot of A 2 against z is curved. Over a limited molecular weight range A 2 may be approximated by a formula of the form A 2 = Cz - ε , (ii) where C is constant for a given polymer-solvent system, ε depends upon z and lies between — ∞ and ½. If A 2 is positive, ε goes from 0 to ½ as z goes from 0 to ∞ and A 2 decreases slowly with z . For systems in which A 2 is negative, ε goes from 0 to — ∞ as z goes from 0 to ∞ and | A 2 | increases extremely rapidly with z . There are complications if the solutions are not homogeneous with respect to chain length, but it is shown that, with well-fractionated samples, little difficulty should arise if z is replaced by the number average < z > n . The theory is illustrated by applying it to some recently published data on the systems: polystyrene-butanone, polystyrene-toluene, and poly iso butylene - cyclo hexane.

Direct Observation of Chain Lengths and Conformations in Oligofluorene Distributions from Controlled Polymerization by Double Electron-Electron Resonance

2019 ◽  
Author(s):  
Dennis Bücker ◽  
Annika Sickinger ◽  
Julian D. Ruiz Perez ◽  
Manuel Oestringer ◽  
Stefan Mecking ◽  
...  
Keyword(s):  
Chain Length ◽  
Length Distribution ◽  
Catalyst System ◽  
Chain Conformation ◽  
Controlled Polymerization ◽  
Chain Length Distribution ◽  
Electron Resonance ◽  
Double Electron ◽  
The Individual ◽  
Double Electron Electron Resonance

Synthetic polymers are mixtures of different length chains, and their chain length and chain conformation is often experimentally characterized by ensemble averages. We demonstrate that Double-Electron-Electron-Resonance (DEER) spectroscopy can reveal the chain length distribution, and chain conformation and flexibility of the individual n-mers in oligo-(9,9-dioctylfluorene) from controlled Suzuki-Miyaura Coupling Polymerization (cSMCP). The required spin-labeled chain ends were introduced efficiently via a TEMPO-substituted initiator and chain terminating agent, respectively, with an in situ catalyst system. Individual precise chain length oligomers as reference materials were obtained by a stepwise approach. Chain length distribution, chain conformation and flexibility can also be accessed within poly(fluorene) nanoparticles.

Natural variation in rice starch synthase IIa affects enzyme and starch properties

2004 ◽  
Vol 31 (7) ◽  
pp. 671 ◽  
Author(s):  
Takayuki Umemoto ◽  
Noriaki Aoki ◽  
Hongxuan Lin ◽  
Yasunori Nakamura ◽  
Naoyoshi Inouchi ◽  
...  
Keyword(s):  
Amino Acid ◽  
Natural Variation ◽  
Oryza Sativa L ◽  
Length Distribution ◽  
Starch Synthase ◽  
Rice Starch ◽  
Nucleotide Polymorphisms ◽  
Cultivated Rice ◽  
Chain Length Distribution ◽  
Starch Properties

The natural variation in starch synthase IIa (SSIIa) of rice (Oryza sativa L.) was characterised using near-isogenic lines (NILs). SSIIa is a candidate for the alk gene regulating the alkali disintegration of rice grains, since both genes are genetically mapped at the same position on chromosome 6 and related to starch properties. In this study, we report that the alkali-susceptible cultivar Nipponbare lacked SSIIa activity in endosperm. However, the activity was detected with NILs having the alk allele of alkali-tolerant Kasalath. SSIIa protein was present even in Nipponbare endosperm, but it was not associated with starch granules at the milky stage of endosperm. Three single-nucleotide polymorphisms (SNPs) predicting amino acid substitutions existed between the cDNA sequences of SSIIa of Nipponbare and Kasalath were genotyped with 65 rice cultivars and four wild relatives of cultivated rice. The results obtained explain the potential importance of two of the amino acid residues for starch association of rice SSIIa. An analysis of the chain-length distribution of β-limit dextrin of amylopectin showed that without SSIIa activity, the relative number of A-chains (the short chains without branches) increased and that of B1-chains (the short chains with branches) decreased. This suggests that, given the SSIIa defect, short A-chains could not reach a sufficient length for branching enzymes to act on them to produce B1-chains.

scholarly journals Miniaturized Analysis of Amylopectin Chain Length Distribution by Fluorescence-Assisted Capillary Electrophoresis (FACE) down to Single Starch Granules

2021 ◽  
Author(s):  
amandine pruvost ◽  
stanislas helle ◽  
nicolas szydlowski ◽  
Christian ROLANDO
Keyword(s):  
Capillary Electrophoresis ◽  
Chain Length ◽  
Solid Phase ◽  
Potato Starch ◽  
Relative Proportion ◽  
Length Distribution ◽  
Fluorescence Analysis ◽  
Starch Granules ◽  
Chain Length Distribution ◽  
Single Granule

In the present work, we developed a miniaturized method for determining amylopectin chain length distribution (CLD) by fluorescence-assisted capillary electrophoresis (FACE). The method relies on single granule entrapping into capillaries followed by direct starch gelatinization and amylopectin debranching on carbograph-based solid phase extraction (SPE) cartridges. Sample desalting on HypersepTM tips following APTS-labelling and the use of nanovials allowed for the fluorescence analysis of weakly diluted samples. Consequently, method sensitivity was improved by 500-fold which is compatible with the analysis of single potato starch granules. The method was implemented to determine CLD profiles of single starch granules ranging from 50 to 100 µm in diameter. In these experiments, the relative proportion of starch glucans of up to 30 degrees of polymerization (DP) could be quantified.

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