Oligomers end-groups

The analysis of the infrared spectrum of this class of materials in the pristine state shows, as expected, little effect of chain length on the IR-active vibrations. From the infrared spectra of the oligomers, end-group modes have been located and, as a consequence. A = 0 phonons of PPV as a one-dimensional lattice have been clearly identified. The frequency shifts from the oligomers to the polymer are extremely small, thus showing that (1) intramolecular coupling as shown by the IR-active modes is small, (2) phonon dispersion curves must be substantially flat, and (3) force constants are not dependent on chain length [234]. 

A rather analog adjustment to represent the accelerating influence of protons can be made for fhe oxidafion of oligomer end groups ... 

Very varied applications have been proposed soil release properties of easy care cotton, assymetric solvents for the resolution of racemates and ligand exchange chromatography, " flame retardant properties, polymeric dyes which were reviewed by Marechal, chemical modification of surfaces, " chelating resins, photoresponsive polymers, " modification of polymers to alter or to remove unstable groups " and photoresists. " Chemical modification of telechelic oligomer end groups is of major importance to increase their reactivity and their selectivity. ... 

Polyester composition can be determined by hydrolytic depolymerization followed by gas chromatography (28) to analyze for monomers, comonomers, oligomers, and other components including side-reaction products (ie, DEG, vinyl groups, aldehydes), plasticizers, and finishes. Mass spectroscopy and infrared spectroscopy can provide valuable composition information, including end group analysis (47,101,102). X-ray fluorescence is commonly used to determine metals content of polymers, from sources including catalysts, delusterants, or tracer materials added for fiber identification purposes (28,102,103). 

A typical maleimide resin is synthesized by the Michael addition of MDA and BMI (Fig. 4). If the stoichiometrically equal amounts of MDA and BMI are added into the reaction solvent under controlled temperature, linear, high molecular weight polyaminoimide (PAI) results. To obtain crosslinkable oligomer (pre-polymer) with maleimide end groups, a calculated 1.1-1.8 times an excess... 

As it was shown in73, 74), methods that can be used to synthesize these copolymers of PAN are those of radical AN block copolymerization in the presence of an oxidation-reduction system in which the hydroxyl end groups of polyethylene oxide) (PEO)73) and polypropylene oxide) (PPO)74- oligomers serve as the reducing agents and tetravalent cerium salts as the oxidizing agents. 

General structure of the (Si—X) terminated siloxane oligomers and a list of important reactive functional end groups (X) are given in Table 2. 

Table 2. General structure of (Si—X) terminated organosiloxane oligomers and important functional end groups...

Determined by end-group titration b Average number of siloxane (Si—O) repeat units in the oligomer ... 

In both of the above techniques the reactive end-groups on siloxane oligomers were directly bonded to the terminal silicon atoms [i.e. Si—Cl and Si—N(CH3)2 respectively]. Therefore the resultant siloxane carbonate copolymers contained (Si—O—C)... 

Siloxane-urea copolymers were synthesized by the reaction of the aminopropyl terminated PDMS oligomers with MDI or HMDI with no chain extenders (Reaction Scheme XI and Tables 14 and 15). Therefore, in these copolymers the hard segments consist of the aminopropyl end groups on the siloxane oligomers and MDI or HMDI backbones as shown below. The soft segment is pure polydimethylsiloxane. 

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