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1.
Cyclomatrix phosphazene–triazine network polymers were synthesized by co‐curing a blend of tris(2‐allylphenoxy), triphenoxy cyclotriphosphazene (TAP), and tris(2‐allylphenoxy) s‐triazine (TAT) with bis(4‐maleimido phenyl) methane (BMM). The co‐curing of the three‐component resin was investigated by dynamic mechanical analysis using rheometry. The cure kinetics of the Diels–Alder step was studied by examining the evolution of the rheological parameters, such as storage modulus (G′), loss modulus (G″), and complex viscosity (η*), for resins of varying compositions at different temperatures. The curing conformed to an overall second‐order phenomenological equation, taking into account a self‐acceleration effect. The kinetic parameters were evaluated by multiple‐regression analysis. The absence of a definite trend in the cure process with blend composition ratio was attributed to the occurrence of a multitude of competitive reactions whose relative rates depend on the reactant ratio and the concentration of the products formed from the initial phase of reaction. The cure was accelerated by temperature for a given composition, whereas the self‐acceleration became less prominent at higher temperature. Gelation was accelerated by temperature. The gel conversion decreased with increase in maleimide concentration and, for a given composition, it was independent of the cure temperature. The activation energy for the initial reaction and the crosslinking process were estimated for a composition with a maleimide‐to‐allyl ratio of 2 : 1. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 908–914, 2003 相似文献
2.
Gabino A. Carriedo Francisco J. García Alonso Alejandro Presa Soto 《Journal of Inorganic and Organometallic Polymers and Materials》2007,17(2):399-406
The chiral phosphazene copolymers {[NP(O2C12H8)]0.9[NP(O2C20H12)]0.1} (1) and {[NP(O2C12H8)]0.9[NP(O2C20H10Br2)]0.1}
n
(2) [(O2C12H8) = 2,2′-dioxy-1,1′-biphenyl; (O2C20H12) = R-2,2′-dioxy-1,1′-binaphthyl and (O2C20H10Br2) = R-6,6′-dibromo-2,2′-dioxy-1,1′-binaphthyl] were prepared by sequential substitution from [NPCl2]
n
and the corresponding dihydroxy-biphenyl or binaphthyl reagents in the presence of Cs2CO3 and K2CO3. The reaction of (2) with tBuLi in THF, followed by addition of PPh2Cl and a treatment with SiHCl3/PPh3 to eliminate any oxidized OC6H4P(O)Ph2 groups, gave the phosphine containing copolymer {[NP(O2C12H8)]0.9[NP(O2C20H10[PPh2]2)]0.1}
n
(3), that was used as a chiral ligand to support [Ru(p-cymene)Cl] complexes. The resulting catalyst was active for hydrogen
transfer from isopropyl alcohol to acetophenone but the placement of the Ru centers in the 6,6′-positions of the binaphthoxyphosphazene
units induced no enantioselectivity.
Dedicated to Professor Christopher Allen. 相似文献
3.
4.
The thermal stabilities of four fluoroelastomers, a polyphosphazene elastomer and four polysiloxanes, mainly in the vulcanised state, have been compared by isothermal weight loss experiments in nitrogen, or in air. The overall activation energies for degradation as a function of percentage conversion to volatiles have also been determined. In the majority of cases there was a linear relationship between activation energy and percentage conversion but the slope may be positive, negative or zero. 相似文献
5.
Nicholas R. Krogman Arlin L. Weikel Nhu Q. Nguyen Katherine A. Kristhart Syam P. Nukavarapu Lakshmi S. Nair Cato T. Laurencin Harry R. Allcock 《应用聚合物科学杂志》2010,115(1):431-437
New biomedically erodible polymer composites were investigated. Polyphosphazenes containing the dipeptide side groups alanyl–glycine ethyl ester, valinyl–glycine ethyl ester, and phenylalanyl–glycine ethyl ester were blended with poly(lactide‐co‐glycolide) (PLGA) with lactic to glycolic acid ratios of 50 : 50 [PLGA (50 : 50)] and 85 : 15 [PLGA (85 : 15)] with solution‐phase techniques. Each dipeptide ethyl ester side group contains two N? H protons that are capable of hydrogen bonding with the carbonyl functions of PLGA. Polyphosphazenes that contain only the dipeptide ethyl ester groups are insoluble in organic solvents and are thus unsuitable for solution‐phase composite formation. To ensure solubility during and after synthesis, cosubstituted polymers with both dipeptide ethyl ester and glycine or alanine ethyl ester side groups were used. Solution casting or electrospinning was used to fabricate polymer blend matrices with different ratios of polyphosphazene to polyester, and their miscibilities were estimated with differential scanning calorimetry and scanning electron microscopy techniques. Polyphosphazenes with alanyl–glycine ethyl ester side groups plus the second cosubstituent were completely miscible with PLGA (50 : 50) and PLGA (85 : 15) when processed via solution‐casting techniques. This suggests that the hydrogen‐bonding protons in alanyl–glycine ethyl ester have access to the oxygen atoms of the carbonyl units in PLGA. However, when the same pair of polymers was electrospun from solution, the polymers proved to be immiscible. Solution‐cast miscible polymer blends were obtained from PLGA (50 : 50) plus the polyphosphazene that was cosubstituted with valinyl–glycine ethyl ester and glycine ethyl ester side groups. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
6.
Christopher W. Allen 《Journal of Inorganic and Organometallic Polymers and Materials》2007,17(2):341-348
A short review of the origins and development of my research program at the University of Vermont in the area of inorganic
polymers is presented. The topics include the discovery of a class of hybrid polymers and copolymers in which an inorganic
ring such as a cyclophosphazene or cycloborazine system is a substituent on a carbon polymer chain. The subsequent elucidation
of the electronic and chemical reactivity factors which control the formation of these materials allowed for design of successive
generations of improved materials. Additional topic includes work in polyphosphazenes which have substituents with exploitable
organic functionality. 相似文献
7.
Paul Strasser Bianca Montsch Silvia Weiss Haider Sami Christoph Kugler Sonja Hager Hemma Schueffl Robert Mader Oliver Brüggemann Christian R. Kowol Manfred Ogris Petra Heffeter Ian Teasdale 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(22):2300767
Bottlebrush polymers are highly promising as unimolecular nanomedicines due to their unique control over the critical parameters of size, shape and chemical function. However, since they are prepared from biopersistent carbon backbones, most known bottlebrush polymers are non-degradable and thus unsuitable for systemic therapeutic administration. Herein, we report the design and synthesis of novel poly(organo)phosphazene-g-poly(α-glutamate) (PPz-g-PGA) bottlebrush polymers with exceptional control over their structure and molecular dimensions (Dh ≈ 15–50 nm). These single macromolecules show outstanding aqueous solubility, ultra-high multivalency and biodegradability, making them ideal as nanomedicines. While well-established in polymer therapeutics, it has hitherto not been possible to prepare defined single macromolecules of PGA in these nanosized dimensions. A direct correlation was observed between the macromolecular dimensions of the bottlebrush polymers and their intracellular uptake in CT26 colon cancer cells. Furthermore, the bottlebrush macromolecular structure visibly enhanced the pharmacokinetics by reducing renal clearance and extending plasma half-lives. Real-time analysis of the biodistribution dynamics showed architecture-driven organ distribution and enhanced tumor accumulation. This work, therefore, introduces a robust, controlled synthesis route to bottlebrush polypeptides, overcoming limitations of current polymer-based nanomedicines and, in doing so, offers valuable insights into the influence of architecture on the in vivo performance of nanomedicines. 相似文献
8.
Polyphosphazenes and metal phosphonates have offered better opportunities than other organoinorganic polymers as starting polymers for the synthesis of sulfonated derivatives. Sulfonated organic polymers are well established in many technological applications and are covered by several literature reviews. Organoinorganic sulfonated polymers are rather new and have never been considered as a self-standing class. Yet since ion-containing polymers and organoinorganic polymers are expanding research fields, organoinorganic sulfonated polymers are likely to attain more attention in the future. The present review therefore covers the synthesis, structure, and properties of sulfonated polyphosphazenes and sulfonated metal phosphonates, in order to indicate what may be expected from organoinorganic polymers functionalized in this fashion.Presented at the 1st Italian Workshop on Cyclo- and Polytphosphazenen Materials. February 15 16, 1996, at the CNR Research Area in Padova, Italy. 相似文献
9.
C. Díaz M. L. Valenzuela 《Journal of Inorganic and Organometallic Polymers and Materials》2006,16(4):419-435
Co-polyphosphazenes containing anchored organometallic fragments are useful precursors for nanostructured metallic materials.
Pyrolysis in air at 800°C yields metallic nanoparticles of the type, M°/M
x
O
y
/M
z
(P
x
O
y
)/P4O7, depending on the metal used; i.e., M° when the metal is a noble metal, metal oxide when the metal is Cr, W and Ru, metallic
pyrophosphate when M = Mn and Fe. The organic spacer of the polyphosphazene influences strongly the morphology of the pyrolytic
product. The mechanism of formation of the nanostructured materials involves carbonization of the organic matter, which produces
holes where the nanoparticles are grown. Reaction of the phosphorus polymeric chain with O2 yield phosphorus oxide units, which act as a P4O7 matrix to stabilize the nanoparticles and/or P
x
O
y
−n
for the formation of metallic pyrophosphates. The method appears to be a general and versatile new route to metallic nanostructured
materials.
Dedicated to Professor Harry Allcock for his pioneering and persevering work on Polyphosphazene and their projection in another
field as materials and recently nanomaterials. 相似文献
10.
Harry R. Allcock 《Journal of Inorganic and Organometallic Polymers》1992,2(2):197-211
Polyphosphazenes are some of the most diverse inorganic-type polymers known. Their molecular and materials diversity is a consequence of the macromolecular substitution method used for their synthesis. This allows a wide range of properties to be designed into the system, and it underlies the emerging technology based on these polymers. 相似文献