Effects of Nanoscale Confinement and Interfaces on the Glass Transition Temperatures of a Series of Poly(n-methacrylate) Films

2007 ◽  
Vol 60 (10) ◽  
pp. 765 ◽  
Author(s):  
Rodney D. Priestley ◽  
Manish K. Mundra ◽  
Nina J. Barnett ◽  
Linda J. Broadbelt ◽  
John M. Torkelson
Keyword(s):  
Glass Transition ◽  
Free Surface ◽  
Surface Effect ◽  
Single Layer ◽  
Butyl Methacrylate ◽  
Hydroxyl Groups ◽  
Substrate Effect ◽  
Transition Temperatures ◽  
Glass Transition Temperatures ◽  
Bilayer Films

We use fluorescence from dye-labelled polymer to measure the glass transition temperatures (Tgs) across single-layer films and near surfaces and silica interfaces in bilayer films for a series of poly(n-methacrylate)s. With nanoscale confinement, the average Tg across a film supported on silica increases for poly(methyl methacrylate) (PMMA), decreases for poly(ethyl methacrylate) (PEMA) and poly(propyl methacrylate), and is nearly invariant for poly(iso-butyl methacrylate) (PIBMA). These trends are consistent with the relative strengths of local perturbations to Tg caused by surfaces and substrates as measured in bilayer films. The substrate effect, which increases Tg via hydrogen-bonding interactions between the polymer and hydroxyl groups on the silica surface, is stronger than the free-surface effect in PMMA. The free-surface effect, which reduces Tg via a reduction in the required cooperativity of the glass transition dynamics, is stronger than the substrate effect in PEMA. The substrate and free-surface effects have similar strengths in perturbing the local Tg in PIBMA, resulting in a net cancellation of effects when measurements are made across single-layer films.

Glass Transition Behavior of Polyisoprene: The Influence of Molecular Weight, Terminal Hydroxy Groups, Microstructure, and Chain Branching

1982 ◽  
Vol 55 (1) ◽  
pp. 245-252 ◽  
Author(s):  
C. Kow ◽  
M. Morton ◽  
L. J. Fetters ◽  
N. Hadjichristidis
Keyword(s):  
Molecular Weight ◽  
Differential Scanning Calorimetry ◽  
Glass Transition ◽  
Low Molecular Weight ◽  
Hydroxyl Groups ◽  
Transition Temperatures ◽  
Scanning Calorimetry ◽  
Chain Branching ◽  
Glass Transition Temperatures ◽  
Hydroxy Groups

Abstract The glass transition temperatures for a series of high-1,4 linear and star-branched polyisoprenes have been measured by differential scanning calorimetry. The Fox-Flory relation for the linear polyisoprenes was found to be Tg=Tg∞−1.76×104Mn−1. The influence of hydroxyl groups on Tg was also examined for low molecular weight (<2.2×104) polyisoprenes.

Designing, characterization, and thermal behavior of triazine-based dendrimers

2015 ◽  
Vol 35 (1) ◽  
pp. 41-52 ◽  
Author(s):  
Dhaval G. Gajjar ◽  
Rinkesh M. Patel ◽  
Hema N. Patel ◽  
Pravinkumar M. Patel
Keyword(s):  
Glass Transition ◽  
Thermal Behavior ◽  
Pamam Dendrimer ◽  
Hydroxyl Groups ◽  
Ionization Mass ◽  
Transition Temperatures ◽  
Scanning Calorimetry ◽  
Glass Transition Temperatures ◽  
Fourier Transform Ir ◽  
C Nmr

Abstract Different generations of dendritic architecture with piperazine in core moiety and hydroxyl groups on the periphery were designed by divergent method. 1,4-biz(4,6-trichloro-1,3,5-triazin-2-yl)piperazine was synthesized as a core for dendrimer synthesis. Dendrimer was then grown to G3 from core compound using diethanolamine and cyanuric chloride as branching units. Dendrimer generations were characterized by infrared (IR) spectroscopy [Fourier transform IR (FTIR)], 1H-nuclear magnetic resonance (NMR), 13C-NMR, electrospray ionization-mass spectrometry (ESI-MS), and elemental analysis. The thermal behavior of both full- and half-generation dendrimers was investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The TGA study revealed that dendrimer generations had a moderate thermal stability. Chlorine-terminated half-generation dendrimers were thermally more stable than hydroxyl-terminated full-generation dendrimers. The DSC technique was employed to determine the glass transition temperatures (Tg) of dendrimer generations. It was observed that the glass transition temperatures of synthesized dendrimer generations were of low value, which is similar to the values reported for the polyamidoamine (PAMAM) dendrimer of the same generation. It was also observed that, with the increase in the molecular weight or generation number of dendrimer, the glass transition temperature was also increased.

Properties of Random PSF/PES Copolymers as High-Performance Polymers

2011 ◽  
Vol 217-218 ◽  
pp. 1606-1610
Author(s):  
Dong Jiang ◽  
Xiao Ran Zhang ◽  
Yan Mei Ma ◽  
Cheng You Ma
Keyword(s):  
Weight Loss ◽  
Tensile Strength ◽  
Glass Transition ◽  
High Performance ◽  
Molar Ratio ◽  
Transition Temperatures ◽  
Elongation At Break ◽  
Glass Transition Temperatures ◽  
High Performance Polymers ◽  
Diphenyl Sulfone

A series of random polysulfone/polyethersulfone (PSF/PES) copolymers were synthesized by the polycondensation of 4, 4'-isopropylidendiphenol, 4, 4΄-dihyolroxy diphenyl sulfone and 4, 4'-dichlorodiphenyl sulfone in the presence of K2CO3. We obtained a series of copolymers by changing the molar ratio of 4, 4΄-dihyolroxy diphenyl sulfone and 4, 4'-isopropylidendiphenol (it was marked as the ratio of S:A). The copolymers have the similar solubility with polyethersulfone. They also have high glass transition temperatures (Tg: 199°C~229°C) and 5% weight loss temperatures (4, 4'-isopropylidendiphenol: 4, 4΄-dihyolroxy diphenyl sulfone=1:1, Td5=497°C). At the same time the elongation at break is much higher than that of PES, while the tensile strength is a little lower than that of PES.

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