The Calculation of Weight Average Molecular Weights during the Course of Decomposition of Homogeneous Linear Polymers

1940 ◽  
Vol 62 (5) ◽  
pp. 1196-1198 ◽  
Author(s):  
Walter H. Durfee ◽  
Z. I. Kertesz
Keyword(s):  
Linear Polymers ◽  
Molecular Weights ◽  
Homogeneous Linear

The Molecular Weights of Rubber and Related Materials. V. The Interpretation of Molecular Weight Measurements on High Polymers

1945 ◽  
Vol 18 (1) ◽  
pp. 1-7
Author(s):  
Geoffrey Gee
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Convenient Method ◽  
Weight Distribution ◽  
Linear Structure ◽  
Linear Polymers ◽  
Viscosity Measurements ◽  
Molecular Weights ◽  
Homogeneous Linear ◽  
Weight Data

Abstract Unless an ultracentrifuge is available, absolute molecular weight determinations must be based ultimately on osmotic data. Viscosity measurements furnish a convenient method of interpolation, and give reliable results for homogeneous linear polymers. The viscosity molecular-weight of a typical unfractionated polymer would not be very seriously in error unless the polymer were extensively branched. No reliable conclusions about molecular-weight distribution can be drawn from molecular-weight data alone without carrying out a fractionation, although a useful guide to the homogeneity of a polymer known to be of linear structure is furnished by the ratio of the viscosity and osmotic molecular weights.

Structure of Polybutadienes

1967 ◽  
Vol 40 (5) ◽  
pp. 1529-1543 ◽  
Author(s):  
W. S. Bahary ◽  
D. I. Sapper
Keyword(s):  
Light Scattering ◽  
Molecular Size ◽  
Structural Features ◽  
Melting Point Depression ◽  
Linear Polymers ◽  
Long Chain Branching ◽  
Molecular Weights ◽  
Catalyst Systems ◽  
Molecular Size Distribution

Abstract Polybutadienes made with six different catalyst systems were examined: (1) butyllithium, (2) “nickel-based”, (3) alfin, (4) “titanium-based”, (5) “cobalt-based”, and (6) free radical emulsion. The microstructure and macrostructure of the polybutadienes have been determined and are compared to the results published in the literature. These polybutadienes may be considered to be random terpolymers of cis, trans, and vinyl addition of butadiene. The glass transition temperature is specified by the vinyl content. The crystalline melting points of the high trans and also the high cis polybutadienes obey to a high measure Flory's equation for melting point depression of a random terpolymer. The molecular weights of the polybutadienes have been determined by light scattering and osmometry and the degree of long chain branching has been determined by the branching index, 〈g′〉. The macro-structural features of the linear polymers are confirmed by fractionation. However, the polydispersities calculated from fractionation data do not agree with those determined from light scattering and osmometry for the branched samples. The discrepancy is attributed to the method of characterization of the fractions. A distinction is made between molecular weight distribution and molecular size distribution.

scholarly journals Dynamic Dilution Effect in Binary Blends of Linear Polymers with Well-Separated Molecular Weights

2014 ◽  
Vol 47 (21) ◽  
pp. 7653-7665 ◽  
Author(s):  
E. van Ruymbeke ◽  
V. Shchetnikava ◽  
Y. Matsumiya ◽  
H. Watanabe
Keyword(s):  
Dilution Effect ◽  
Linear Polymers ◽  
Binary Blends ◽  
Molecular Weights

Synthesis and Characterization of Linear Polymers for Non-Linear Optics through Click Chemistry Route

2012 ◽  
Vol 584 ◽  
pp. 8-12 ◽  
Author(s):  
Balakrishna Kolli ◽  
Sarada P. Mishra ◽  
Mukesh P. Joshi ◽  
S. Raj Mohan ◽  
T.S. Dhami ◽  
...  
Keyword(s):  
Click Chemistry ◽  
Second Harmonic ◽  
Gel Permeation Chromatography ◽  
Linear Polymers ◽  
Linear Optics ◽  
Scanning Calorimetry ◽  
Force Microscopy ◽  
Molecular Weights ◽  
Non Linear Optics ◽  
Atomic Force

Click chemistry is used for synthesizing polymers for second order NLO study. The molecular weights found by gel-permeation chromatography (GPC), were in the range of 7000-55000 g/mol. Differential scanning calorimetry shows glass transition temperature (Tg) above 120 oC. From electronic spectra order parameter of the poled films were calculated to be 0.1-0.5. The change in surface morphology after poling was checked by atomic force microscopy. By using a pulsed Nd:YAG laser (1064nm), the second harmonic generation (SHG) intensity was measured. The SHG intensity was also studied as a function of against temperature and time respectively.

Synthesis of Radial Thermoplastic Elastomers

1976 ◽  
Vol 49 (5) ◽  
pp. 1305-1310 ◽  
Author(s):  
H. L. Hsieh
Keyword(s):  
Coupling Reaction ◽  
Shear Resistance ◽  
Thermoplastic Elastomers ◽  
Lower Solution ◽  
Commercial Production ◽  
Linear Polymers ◽  
Block Sequence ◽  
Block Polymers ◽  
Molecular Weights ◽  
Number Of Branches

Abstract The combination of anionic polymerization techniques and a subsequent coupling reaction created a versatile process for producing block polymers of not only controlled block length and block sequence but also with a controlled number of branches. This process has been successfully used in commercial production since 1967. Radial styrene-diene block polymers have properties significantly different from linear polymers of the same molecular weight, showing lower melt viscosities as well as lower solution viscosities. This feature is significant in adhesive applications because it allows the use of polymers of higher molecular weights with a corresponding improvement in shear resistance.

Synthesis and characterization of macrocyclic poly(.-methylstyrene)

e-Polymers ◽  
2001 ◽  
Vol 1 (1) ◽  
Author(s):  
Dahai Dong ◽  
Thieo E. Hogen-Esch
Keyword(s):  
Size Exclusion ◽  
Careful Study ◽  
Coupling Reactions ◽  
Linear Polymers ◽  
High Dilution ◽  
Fractional Precipitation ◽  
Molecular Weights ◽  
Vinyl Polymers ◽  
High Concentrations

AbstractThe synthesis is described of macrocyclic poly(α-methylstyrene) (PAMS) by the lithium naphthalide initiated polymerization of AMS followed by high dilution end to end coupling with 1,4-bis(bromomethyl)benzene (DBX). The cyclization is carried out by simultaneous addition of tetrahydrofuran solutions of the PAMS dianion and DBX at about -100ºC. A sample of the matching linear PAMS is obtained by protonation of the PAMS dianion. The purified cycles are obtained by fractional precipitation that is monitored by size exclusion chromatograhy. A careful study of the coupling reactions carried out at high concentrations indicates that coupling is efficient and this is borne out by the ratios (<G>) of apparent molecular weights (MW’s) of cycles and matching linear polymers. The <G> values of the cycles tend to vary with MW in the same manner as was demonstrated for polystyrene and other vinyl polymers and increase from around 0.74 at MW of about 30000 to values of around 0.82 at MW of about 2500. A higher apparent <G> value was observed for a very low MW PAMS but this sample could not be purified and analyzed adequately. As was also observed for other macrocyclic vinylpolymers, the glass transition temperatures of the cycles are MW independent above MW of about 5000 but decrease sharply at lower MW’s.

scholarly journals Molecular Growth Pathways in Silica Sol-Gel Polymerization

1988 ◽  
Vol 121 ◽  
Author(s):  
W. G. Klemperer ◽  
S. D. Ramamurthi
Keyword(s):  
Sol Gel ◽  
Molecular Size ◽  
Weight Fraction ◽  
Degree Of Polymerization ◽  
Partial Hydrolysis ◽  
Linear Polymers ◽  
Mole Percent ◽  
Molecular Weights ◽  
Low Degree ◽  
Acidic Conditions

ABSTRACTCapillary gas chromatography has been used to monitor the stoichi-ometries, structures, and abundances of low molecular weight polysilicate esters formed by partial hydrolysis of methanolic tetramethylorthosili-cate and redistribution of methanolie hexamethyoxydisiloxane under acidic (HC1) and basic (KOH) conditions. The polysilicate molecular size distributions, expressed in terms of mole percent of total silicon present as a function of degree of polymerization, show maxima near the number average degree of polymerization under acidic conditions. Under basic conditions, the distribution has its maximum at the monomer percent and extends to very high molecular weights, yielding a distribution far broader than the one observed under acidic conditions. These features are in agreement with covalent network theories of silica gelation, as opposed to particle aggregation theories. Weight fraction distributions of the type observed under acidic conditions are characteristic of linear polymers with a low degree of crosslinking and weight fraction distributions of the type observed under basic conditions are characteristic of branched polymers with high degree of crosslinking. The low degree of crosslinking obtained under acidic conditions is observed to arise from steric crowding that discourages branching in polysilicate structures.

The Nature of the Dynamic Double Refraction of Rubber Solutions and the Shape of Rubber Molecules

1946 ◽  
Vol 19 (2) ◽  
pp. 360-384 ◽  
Author(s):  
V. Tsvetkov ◽  
A. Petrova
Keyword(s):  
Experimental Data ◽  
Electric Field ◽  
Optical Constant ◽  
Linear Polymers ◽  
Double Refraction ◽  
Flowing Liquid ◽  
Elastic Effect ◽  
Molecular Weights ◽  
Synthetic Rubber ◽  
Wide Range

Abstract The work which is described in the present paper is concerned with the development of a method for measuring the double refraction of a flowing liquid, with particular attention to a study of the structure of polymers. The dependence of double refraction and of the angle of extinction on the velocity of flow of solutions of thirty samples of synthetic rubber through a wide range of velocities was studied. For linear polymers having high molecular weights, the relation: Δn=ƒ(g), shows, when represented graphically, an ascending concave curve. This relation is rectilinear for all polymers whose molecular weights lie within the usual range. In all cases investigated, the angle of extinction lay within the limits of 45° and 0°. The dynamic optical constant which characterizes the double refraction of rubber was established experimentally. This dynamic optical constant was calculated for all samples of rubbers which were studied. Three effects on the double refraction of a solution of a polymer during flow were distinguished experimentally: (1) the effect of the shape of the particles; (2) the effect of the anisotropy of the particles ; and (3) the elastic effect. The double refraction of solutions of synthetic rubbers in an electric field was investigated with a view to determining the anisotropy of the molecules of the polymers. On the basis of the experimental data it is concluded that the double refraction of a flowing rubber solution is fundamentally influenced by the effect of tension. The theory of Kuhn and the experimental data obtained in the present work were utilized to calculate the relation between the transverse and longitudinal dimensions of all the rubbers which were studied.

A method for the determination of number average molecular weights of linear polymers less than 5 000

Polymer ◽  
1967 ◽  
Vol 8 ◽  
pp. 269-271 ◽  
Author(s):  
D. Margerison ◽  
Miss V.A. Nyss ◽  
Mrs E. Pulat
Keyword(s):  
Linear Polymers ◽  
Molecular Weights
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