Impacts of Polystyrene Molecular Weight and Modification to the Repeat Unit Structure on the Glass Transition−Nanoconfinement Effect and the Cooperativity Length Scale

2005 ◽  
Vol 38 (5) ◽  
pp. 1767-1778 ◽  
Author(s):  
Christopher J. Ellison ◽  
Manish K. Mundra ◽  
John M. Torkelson
Keyword(s):  
Molecular Weight ◽  
Glass Transition ◽  
Repeat Unit ◽  
Length Scale ◽  
Unit Structure

scholarly journals Molecular weight and end capping effects on the optoelectronic properties of structurally related ‘heavy atom’ donor–acceptor polymers

2014 ◽  
Vol 2 (35) ◽  
pp. 14468-14480 ◽  
Author(s):  
Gregory L. Gibson ◽  
Dong Gao ◽  
Ashlee A. Jahnke ◽  
Jing Sun ◽  
Andrew J. Tilley ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Repeat Unit ◽  
Heavy Atom ◽  
Optoelectronic Properties ◽  
Morphological Properties ◽  
Group Differences ◽  
Unit Structure ◽  
Donor Acceptor ◽  
End Capping ◽  
End Group

Molecular weight and end group differences produce distinct optoelectronic and morphological properties in heavy atom donor–acceptor polymers of the same repeat unit structure.

The effect of methyl and methoxy substituents on dianilines for a thermosetting polyimide system

2020 ◽  
Vol 32 (7) ◽  
pp. 801-822 ◽  
Author(s):  
John J La Scala ◽  
Greg Yandek ◽  
Jason Lamb ◽  
Craig M Paquette ◽  
William S Eck ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Molecular Weight ◽  
Glass Transition ◽  
Elevated Temperature ◽  
Methyl Substituent ◽  
Glass Transition Temperatures ◽  
High Performing ◽  
Methoxy Substituent ◽  
Acidic Conditions ◽  
Thermal Stability Of

4,4′-Methylenedianiline (MDA) is widely used in high-temperature polyimide resins, including polymerization of monomer reactants-15. The toxicity of MDA significantly limits the manufacturability using this resin. Modifying the substitution and electronics of MDA could allow for the reduction of toxicity while maintaining the high-performing properties of the materials derived from the modified MDA. The addition of a single methyl substituent, methoxy substituent, location of these substituents, and location of the amine relative to the phenolic bridge were modified as were other non-aniline diamines. Various anilines were condensed with paraformaldehyde under acidic conditions to yield dianilines. These dianilines and diamines were reacted with nadic anhydride and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride in methanol to form the polyamic acid oligomers and heated at elevated temperature to form polyimide oligomers. It was found that the molecular weight of the oligomers derived from MDA alternatives was generally lower than that of MDA oligomers resulting in lower glass transition temperatures ( T gs) and degradation temperatures. Additionally, methoxy substituents further reduce the T g of the polymers versus methyl substituents and reduce the thermal stability of the resin. Methyl-substituted alternatives produced polyimides with similar T gs and degradation temperatures. The toxicity of the MDA alternatives was examined. Although a few were identified with reduced toxicities, the alternatives with properties similar to that of MDA also had high toxicities.

Stereo-chemical contributions to the glass transition and liquid–liquid phase separation in high molecular weight poly(N-vinyl carbazole)

RSC Advances ◽  
2016 ◽  
Vol 6 (35) ◽  
pp. 29326-29333 ◽  
Author(s):  
Abdul G. Al Lafi ◽  
James N. Hay
Keyword(s):  
Molecular Weight ◽  
Glass Transition ◽  
Phase Separation ◽  
Liquid Phase ◽  
High Molecular Weight ◽  
Structural Properties ◽  
Thermal History ◽  
Liquid Phase Separation ◽  
High Molecular Weight Poly ◽  
Liquid Liquid Phase Separation

Thermal history and purification effects on the structural properties of PVK were investigated. Liquid–liquid phase separation is suggested to occur by separation of isotactic rich segments from a matrix which is predominantly atactic.

Synthesis and Characterization of Poly(Aryl Ether Quinoxaline)s with Controlled Molecular Weight

2011 ◽  
Vol 391-392 ◽  
pp. 826-829
Author(s):  
Song Ya Zhang ◽  
Zhong Xiao Li ◽  
Jia Ling Pu
Keyword(s):  
Molecular Weight ◽  
Glass Transition ◽  
Strong Acid ◽  
Decomposition Temperature ◽  
Molar Ratio ◽  
Synthesis And Characterization ◽  
Aryl Ether ◽  
Good Solubility ◽  
Step Procedure

Novel poly(aryl ether quinoxaline)s (PEQs) were prepared via a two-step procedure. First, poly (ether benzil) (PEB) was synthesized by the polycondensation of 4,4’-difluorobenzil and 4,4’-isopropylidenediphenol.Then, PEB was reacted with 1,2-diaminobenzene and 4,4'-oxydibenzene-1,2-diamine to give the PEQs. The molecular weight of the PEQs could be adjusted easily by varying the molar ratio of 1,2-diaminobenzene to 4,4'-oxydibenzene-1,2-diamine. The PEQs exhibited good solubility in common organic solvents such as NMP, DMAc, DMF, cyclohexanone and chloroform. In addition, the PEQs also had high glass transition (Tg) temperatures and good thermal properties, with an initial thermal decomposition temperature above 475 oC and glass transition temperatures above 210 oC. They also exhibited excellent resistance to strong acid and alkali.

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