Search results for "polycarbonate"
showing 10 items of 79 documents
Controlled Synthesis of Multi-Arm Star Polyether-Polycarbonate Polyols Based on Propylene Oxide and CO2
2013
Multi-arm star copolymers based on a hyperbranched poly(propylene oxide) polyether-polyol (hbPPO) as a core and poly(propylene carbonate) (PPC) arms are synthesized in two steps from propylene oxide (PO), a small amount of glycidol and CO2 . The PPC arms are prepared via carbon dioxide (CO2 )/PO copolymerization, using hbPPO as a multifunctional macroinitiator and the (R,R)-(salcy)CoOBzF5 catalyst. Star copolymers with 14 and 28 PPC arms, respectively, and controlled molecular weights in the range of 2700-8800 g mol(-1) are prepared (Mw /Mn = 1.23-1.61). Thermal analysis reveals lowered glass transition temperatures in the range of -8 to 10 °C for the PPC star polymers compared with linear …
Blends of polyamide 6 and bisphenol-A polycarbonate. Effects of interchange reactions on morphology and mechanical properties
1992
Blends of polyamide 6 (PA6) and polycarbonate (PC) were prepared in a Brabender mixer, at 240°C, applying long mixing time, for 45 min. It was observed that the morphology and the mechanical properties tend to resemble those of a homogeneous material as the mixing time and PA6 concentration increase. This is attributed to chemical reactions taking place between the two homopolymers. Acidolysis, amidolysis, and aminolysis, catalyzed by the terminals and the amide groups of the polyamide, should in principle be possible. Our results indicate that the aminolysis is the main process, inducing simultaneously scission of PC chains and formation of PC-PA6 copolymer chains. The latter act as interf…
Preparative fractionation and characterization of polycarbonate/eugenol-siloxane copolymers
2002
Bisphenol-A polycarbonate/eugenol-siloxane copolymers were fractionated at the preparative scale by the continuous polymer fractionation (CPF) technique. It is the first example of copolymer fractionation by CPF. The distribution of siloxane species across the fractions was assessed for copolymers differing in initial siloxane concentration and block length. On- and off-line combinations of size exclusion chromatography and infrared spectroscopy were used to analyze chemical composition (CC) of the unfractionated samples across the molecular weight distribution enabling comparison with the fractions. A polycarbonate-siloxane copolymer containing 10 wt% of very short siloxane blocks (dp = 2)…
Multiarm Polycarbonate Star Polymers with a Hyperbranched Polyether Core from CO2 and Common Epoxides
2017
Multiarm star copolymers, consisting of hyperbranched poly(ethylene oxide) (hbPEO) or poly(butylene oxide) (hbPBO) polyether copolymers with glycerol branching points as a core, and linear aliphatic polycarbonate arms generated from carbon dioxide (CO2) and epoxide monomers, were synthesized via a “core-first” approach in two steps. First, hyperbranched polyether polyols were prepared by anionic copolymerization of ethylene oxide or 1,2-butylene oxide with 8–35% glycidol with molecular weights between 800 and 389,000 g·mol–1. Second, multiple arms were grown via immortal copolymerization of CO2 with propylene oxide or 1,2-butylene oxide using the polyether polyols as macroinitiators and (R,…
Rigid Hyperbranched Polycarbonate Polyols from CO2 and Cyclohexene-Based Epoxides
2017
Hyperbranched, multifunctional polycarbonate polyols based on CO2, cyclohexene oxide (CHO), and the “inimer” (initiator–monomer) (4-hydroxymethyl)cyclohexene oxide (HCHO) were prepared in one-pot syntheses. The related linear poly(hydroxymethyl cyclohexene carbonate) structures based on protected HCHO and postpolymerization deprotection were also synthesized as model compounds. The content of hydroxyl functionalities was adjustable for both linear and hyperbranched terpolymer systems. All CO2/epoxide polymerizations were catalyzed by the (R,R)-(salcy)-Co(III)Cl complex. The polycarbonates obtained were comprehensively investigated using various 1D and 2D NMR techniques, SEC, FT-IR, UV–vis s…
Influence of processing conditions on rheological and mechanical properties of polycarbonate/polypropylene blends
1987
Abstract Rheological and mechanical data on polycarbonate/polypropylene blends are reported as a function of the blend preparation. Both kinds of properties depend on the properties of the homopolymers and on the processing conditions. In the molten state the blends are compatible at low content of polypropylene and incompatible at high content. The blends with intermediate compositions can be called semicompatible. Also in the solid state the blends with low content of polypropylene are compatible, while all other blends are incompatible.
A new method for data evaluation of small angle neutron scattering experiments and its application to amorphous polycarbonate
1981
The conformation of single chains in bulk polymer materials can be evaluated from coherent neutron scattering on mixtures of normal and deuterated polymers. It is shown that the single-chain structure factor can be also obtained from measurements of highly concentrated mixtures and the procedure of evaluation is described. The application to amorphous polycarbonate demonstrates the advantages of the method.
Dielectric behaviour of a γ-irradiated polycarbonate
1980
Dielectric measurements on a γ-irradiated polycarbonate in a dose range 0–20 Mrad and at test frequencies of 103 and 104 Hz have been carried out. The glass transition temperature shows a maximum at 3.5 Mrad and then decreases at larger doses. This result is in line with other experiments (intrinsic viscosity, dynamic-mechanical measurements, etc) already reported: the Tg values are however larger in the present results. This is probably due to the plasticizing action of the absorbed moisture present in the previous tests. A Tg vs 1/[n]2 plot (1/[n]2 is proportional to 1/m ) allows to find the value of the glass transition point at an infinite molecular weight and the dependency of Tg on mo…
GALACTOSE-DECORATED POLYMERIC CARRIERS FOR HEPATOCYTE-SELECTIVE DRUG TARGETING
2015
In this paper, the current available strategies to realize galactose-decorated nanostructured polymeric systems are summarized. These carriers are designed in order to obtain targeted drug delivery to hepatocytes via galactose (GAL) moieties, i.e., for the treatment of viral hepatitis or liver cancer that are the greater causes of global disability and mortality. Usually, the main followed strategy to obtain galactosylated polymeric carriers is to use galactosylated copolymers. The chemical modifications of preformed polymers with sugar-containing reagents is followed for obtaining lactosaminated human albumin, galactosylated phospholipid-polyaminoacid and polylactide (PLA)- polyaminoacid c…