Thermoplastics Modified with Nanoscale Inorganic Macromers

1998 ◽  
Vol 519 ◽  
Author(s):  
Timothy S. Haddad ◽  
Patrick T. Mather ◽  
Hong G. Jeont ◽  
Angel Romo-Uribe ◽  
Amy R. Farrist ◽  
...  
Keyword(s):  
Storage Modulus ◽  
Mole Fraction ◽  
Inorganic Materials ◽  
Mechanical Relaxation ◽  
Hybrid Copolymers ◽  
Polymer Properties ◽  
Relaxation Temperature ◽  
Unique Approach ◽  
Β Relaxation ◽  
Oligomeric Silsesquioxane

AbstractWe have taken a unique approach to the synthesis and study of hybrid organic/inorganic materials. Our method involves synthesizing nano-size inorganic P1R7Si8O12 clusters which contain seven inert “R” groups for solubility and only one functional “P” group for polymerization. This strategy permits the synthesis of melt processable, linear hybrid polymers containing pendent inorganic clusters and allows us to study the effect these clusters have on chain motions and polymer properties. The synthesis of norbomenyl-based polyhedral oligomeric silsesquioxane (POSS) macromers, their ring opening metathesis copolymerizations with varying amounts of norbornene, and analysis of the effect of the pendent POSS group is presented. The mechanical relaxation behavior and microstructure of norbornyl-POSS hybrid copolymers have been examined for their dependencies on the mole fraction of POSS-norbornyl monomer, as well as for potential sensitivity to the seven inert “R” groups present in each POSS macromer. POSS copolymerization is observed to enhance the α-relaxation temperature, Tα, in proportion to the mole fraction of POSS-norbornyl comonomer. Interestingly, however, the magnitude of this dependence is larger for POSS-norbornyl comonomer possessing cyclohexyl groups (CyPOSS) than for cyclopentyl groups (CpPOSS). While POSS copolymerization yields only slight enhancement of the tensile storage modulus measured near room temperature, at temperatures lower than a strong mechanical relaxation (β-relaxation near T = -75 °C), there is a significant POSS-reinforcement of the storage modulus.

Hybrid Inorganic/Organic Diblock Copolymers. Nanostructure in Polyhedral Oligomeric Silsesquioxane Polynorbornenes.

2000 ◽  
Vol 628 ◽  
Author(s):  
Timothy S. Haddad ◽  
Patrick T. Mather ◽  
Hong G. Jeon ◽  
Seung B. Chun ◽  
Shawn H. Phillips
Keyword(s):  
Ring Opening ◽  
Diblock Copolymers ◽  
Polyhedral Oligomeric Silsesquioxane ◽  
Inorganic Materials ◽  
Polymer Backbone ◽  
Transmission Electron ◽  
Polymer Properties ◽  
Oligomeric Silsesquioxane ◽  
Nano Size ◽  
Oxygen Framework

ABSTRACTOur main approach to the synthesis and study of hybrid organic/inorganic materials involves incorporating nano-size inorganic polyhedral oligomeric silsesquioxane (POSS) clusters into various polymeric resins. A typical POSS cluster is a discrete silicon and oxygen framework solubilized with organic groups and contains a single reactive site. This lone site of reactivity is used to covalently attach the inorganic macromers pendent to a polymer backbone without causing any crosslinking. This strategy permits the synthesis of melt processable, linear hybrid polymers containing pendent inorganic clusters, and allows us to study the effect these clusters have on chain motion, polymer properties and morphology. The synthesis of norbornenyl-based (POSS) macromers, their ring opening metathesis copolymerizations with varying amounts of norbornene, and analysis of the effect of the pendent POSS group is presented. Ring opening metathesis polymerization permits the easy synthesis of both random and diblock copolymers. Transmission electron microscopy (TEM) clearly images POSS-rich domains against the POSS-free regions. Major differences in polymer morphology are observed as the amount of inorganic POSS is varied, between random and diblock copolymers, as well as between polymers that differ only in the solubilizing cycloalkyl groups on the POSS cluster.

Decoupling Temperature–Volume Effects on Poly[2-Methoxy-5-(2′-Ethylhexyloxy)-1,4-Phenylene-Vinylene] Films at the β-Relaxation Temperature

2020 ◽  
Vol 124 (26) ◽  
pp. 5496-5501
Author(s):  
Silésia de Fátima Curcino da Silva ◽  
Maurício Foschini ◽  
José Roberto Tozoni ◽  
Osvaldo N. Oliveira ◽  
Patricia Targon Campana ◽  
...  
Keyword(s):  
Phenylene Vinylene ◽  
Relaxation Temperature ◽  
Β Relaxation ◽  
Volume Effects

scholarly journals Dynamic Mechanical Relaxation in LaCe-Based Metallic Glasses: Influence of the Chemical Composition

Metals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 1013 ◽  
Author(s):  
Minna Liu ◽  
Jichao Qiao ◽  
Qi Hao ◽  
Yinghong Chen ◽  
Yao Yao ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Metallic Glasses ◽  
Physical Aging ◽  
Enthalpy Of Mixing ◽  
Mechanical Analysis ◽  
Mechanical Relaxation ◽  
Atomic Mobility ◽  
Dynamic Mechanical ◽  
Β Relaxation

The mechanical relaxation behavior of the (La0.5Ce0.5)65Al10(CoxCu1−x)25 at% (x = 0, 0.2, 0.4, 0.6, and 0.8) metallic glasses was probed by dynamic mechanical analysis. The intensity of the secondary β relaxation increases along with the Co/Cu ratio, as has been reported in metallic glasses where the enthalpy of mixing for all pairs of atoms is negative. Furthermore, the intensity of the secondary β relaxation decreases after physical aging below the glass transition temperature, which is probably due to the reduction of the atomic mobility induced by physical aging.

scholarly journals Recent Advances in Polyurethane/POSS Hybrids for Biomedical Applications

Molecules ◽  
2021 ◽  
Vol 27 (1) ◽  
pp. 40
Author(s):  
Jan Ozimek ◽  
Krzysztof Pielichowski
Keyword(s):  
Biomedical Applications ◽  
Surface Characteristics ◽  
Inorganic Materials ◽  
Polyhedral Oligomeric Silsesquioxanes ◽  
Cardiovascular Stents ◽  
Fundamental Properties ◽  
Polymer Properties ◽  
Recent Developments ◽  
Bio Imaging ◽  
Material Porosity

Advanced organic-inorganic materials-composites, nanocomposites, and hybrids with various compositions offer unique properties required for biomedical applications. One of the most promising inorganic (nano)additives are polyhedral oligomeric silsesquioxanes (POSS); their biocompatibility, non-toxicity, and phase separation ability that modifies the material porosity are fundamental properties required in modern biomedical applications. When incorporated, chemically or physically, into polyurethane matrices, they substantially change polymer properties, including mechanical properties, surface characteristics, and bioactivity. Hence, this review is dedicated to POSS-PU composites that have recently been developed for applications in the biomedical field. First, different modes of POSS incorporation into PU structure have been presented, then recent developments of PU/POSS hybrids as bio-active composites for scaffolds, cardiovascular stents, valves, and membranes, as well as in bio-imaging and cancer treatment, have been described. Finally, characterization and methods of modification routes of polyurethane-based materials with silsesquioxanes were presented.

Structural Relaxation, “Memory Behaviour”, Specific Heat Anomaly and Localized Motions in Amorphous Solids

1990 ◽  
Vol 215 ◽  
Author(s):  
G. P. Johari
Keyword(s):  
Specific Heat ◽  
Chemical Reactions ◽  
Structural Relaxation ◽  
Amorphous Solids ◽  
Glassy Matrix ◽  
Mechanical Relaxation ◽  
Mechanical Spectroscopy ◽  
Scanning Calorimetry ◽  
Glassy Material ◽  
Β Relaxation

AbstractDielectric and mechanical relaxation spectroscopy of thermoplastics and thermosets show that, in the former, ageing is related only to the spontaneous structural relaxation towards a lower energy, but still disordered, structure and decreases the strength of the β- relaxation process. Ageing of a thermoset initially increases the strength of its (dielectric) β-relaxation as a result of diffusionallowed chemical reactions, which increase the number of dipolar groups, and later decreases it towards a limiting value. The decrease in the strength of β-relaxation on ageing of polymers and other amorphous solids suggests that structural relaxation causes a collapse of low-density, high-entropy, regions or “soft-sites” randomly distributed in the structure of a glassy material. The increase in the strength of β-relaxation observed in thermosets is higher than calculated from the extent of chemical reactions that occur during their structural relaxation at T<Tg. It is suggested that these effects should be included in the phenomenological theories for both the physical ageing and “memory behaviour” - the latter can be conveniently studied by both dielectric and mechanical spectroscopy and by differential scanning calorimetry. Structural relaxation also decreases the magnitude of the specific heat anomaly in amorphous solids and can be used to experimentally test the postulate that tunneling centres involved in the low-temperature phonon properties are related to the presence of “islands of mobility” or “soft-sites” in an otherwise rigid glassy matrix.

scholarly journals Characteristics of Thermosetting Polymer Nanocomposites: Siloxane-Imide-Containing Benzoxazine with Silsesquioxane Epoxy Resins

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2510
Author(s):  
Chih-Hao Lin ◽  
Wen-Bin Chen ◽  
Wha-Tzong Whang ◽  
Chun-Hua Chen
Keyword(s):  
Thermal Expansion ◽  
Storage Modulus ◽  
Polymer Nanocomposites ◽  
Epoxy Resins ◽  
Coefficient Of Thermal Expansion ◽  
Dynamic Mechanical ◽  
Double Decker ◽  
The Matrix ◽  
Thermosetting Polymer ◽  
Oligomeric Silsesquioxane

A series of innovative thermosetting polymer nanocomposites comprising of polysiloxane-imide-containing benzoxazine (PSiBZ) as the matrix and double-decker silsesquioxane (DDSQ) epoxy or polyhedral oligomeric silsesquioxane (POSS) epoxy were prepared for improving thermosetting performance. Thermomechanical and dynamic mechanical characterizations indicated that both DDSQ and POSS could effectively lower the coefficient of thermal expansion by up to approximately 34% and considerably increase the storage modulus (up to 183%). Therefore, DDSQ and POSS are promising materials for low-stress encapsulation for electronic packaging applications.

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