Elastically Effective Strand Density in Polymer Networks

1969 ◽  
Vol 42 (5) ◽  
pp. 1285-1293
Author(s):  
N. R. Langley
Keyword(s):  
Molecular Weight ◽  
Statistical Approach ◽  
Main Chain ◽  
Polymer Network ◽  
Polymer Networks ◽  
Entanglement Density ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Cross Links ◽  
New Criterion

Abstract A new expression is derived which relates the density of elastically effective strands in a polymer network to the densities of random cross-links, main-chain scissions, and entanglements and to the molecular weight distribution of the initial linear polymer. Methods are recommended for characterizing the cross-link and scission densities from measurable sol fractions and for determining the entanglement density empirically. The strand density can be evaluated quite easily for the random and uniform initial molecular weight distributions. The new expression differs appreciably from that of Mullins and Bueche, owing principally to a new criterion for effectively trapping network entanglements. The statistical approach used to derive the strand density is also used in a new derivation of an existing implicit expression for the gel fraction.

Polymerization of Nitrophenyl and 3-Diethylaminophenyl Prop-2-yn-1-yl Ethers with PdCl2. Polymers and Copolymers Characterization

1998 ◽  
Vol 63 (11) ◽  
pp. 1803-1814 ◽  
Author(s):  
Hynek Balcar ◽  
Petr Holler ◽  
Jan Sedláček ◽  
Vratislav Blechta
Keyword(s):  
Molecular Weight ◽  
Dimethyl Sulfoxide ◽  
Size Exclusion Chromatography ◽  
Main Chain ◽  
Size Exclusion ◽  
Low Molecular Weight ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Exclusion Chromatography

2-, 3- and 4-Nitrophenyl prop-2-yn-1-yl ethers were polymerized with PdCl2 in N,N-dimethylformamide (DMF) giving brown polymers soluble in DMF, dimethyl sulfoxide and N-methylpyrrolidone. Broad (mostly bimodal) molecular weight distributions were observed by size-exclusion chromatography (SEC) with maxima at molecular weight of about 4 . 103 and 1 . 105. With the same catalyst, 3-diethylaminophenyl prop-2-yn-1-yl ether gave predominantly low molecular weight homopolymer (Mn = 4 200) soluble in DMF, N-methylpyrrolidone, CHCl3 and tetrahydrofuran-soluble copolymers with 4-nitrophenyl prop-2-yn-1-yl ether (Mn about 3 000). IR, NMR and UV-VIS spectra of prepared polymers and copolymers proved the structure to consist of the polyene-type main chain with phenoxymethyl pendant groups bearing nitro or diethylamino substituents.

The Use of Novel F-RAFT Agents in High Temperature and High Pressure Ethene Polymerization: Can Control be Achieved?

2007 ◽  
Vol 60 (10) ◽  
pp. 788 ◽  
Author(s):  
Markus Busch ◽  
Marion Roth ◽  
Martina H. Stenzel ◽  
Thomas P. Davis ◽  
Christopher Barner-Kowollik
Keyword(s):  
Molecular Weight ◽  
High Pressure ◽  
High Temperature ◽  
Degree Of Polymerization ◽  
Molecular Weight Distributions ◽  
High Pressure High Temperature ◽  
Reversible Addition ◽  
Weight Distributions ◽  
Raft Agent ◽  
Initial Results

Simulations are employed to establish the feasibility of achieving controlled/living ethene polymerizations. Such simulations indicate that reversible addition–fragmentation chain transfer (RAFT) agents carrying a fluorine Z group may be suitable to establish control in high-pressure high-temperature ethene polymerizations. Based on these simulations, specific fluorine (F-RAFT) agents have been designed and tested. The initial results are promising and indicate that it may indeed be possible to achieve molecular weight distributions with a polydispersity being significantly lower than that observed in the conventional free radical process. In our initial trials presented here (using the F-RAFT agent isopropylfluorodithioformate), a correlation between the degree of polymerization and conversion can indeed be observed. Both the lowered polydispersity and the linear correlation between molecular weight and conversion indicate that control may in principle be possible.

Environmentally Benign Adhesive Synthesized by Dispersion Copolymerization of Styrene and Butyl Acrylate

2006 ◽  
Vol 11-12 ◽  
pp. 757-760
Author(s):  
Jun Ying Zhang ◽  
Peng Dou
Keyword(s):  
Molecular Weight ◽  
Butyl Acrylate ◽  
Monomer Concentration ◽  
Environmentally Benign ◽  
Functional Monomer ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Stabilizer Concentration ◽  
Ethanol Medium ◽  
Weight Distributions

Environmentally benign adhesive was synthesized by dispersion copolymerization of styrene(St) and butyl acrylate (BA) in an ethanol medium with benzoyl peroxide (BPO) as the initiator and poly(vinylpyrrolidone) as the stabilizer in the presence of acrylic acid(AA) as the functional monomer. The effect of the concentration of stabilizer, initiator and functional monomer on the conversions, molecular weights and molecular weight distributions was investigated. The results show that the conversions almost keep invariable with the increasing of stabilizer concentration, but the molecular weights increase and molecular weight distributions decrease. Conversions increase with the increasing of initiator concentration, but the molecular weights and molecular weight distributions decrease. However with the increasing of functional monomer concentration, conversions and molecular weight distributions increase but the molecular weights decrease.

Sign in / Sign up

Export Citation Format

Share Document