Alternating copolyester

Cyclic acid anhydrides are highly reactive not only to electrophilic attack but also to nucleophilic attack. Alternating copolyesters were obtained from cyclic acid anhydrides and epoxides at high temperatures261-263. ... 

The examples given in Equations 2(38) and 3(21) are 1 1 alternating copolyesters consisting of two different repeating units linked to each other alternatively. In order to prepare the desired polyesters the triad monomer has to be synthesized first via a multi-step route that will be described in the next section. 

The example given in Equation 5(39) is a special kind copolyester of alternating sequence. Since the" two monomers, 4-hydroxyben-zoic acid and 6-hydroxy-2-naphthoic acid, can undergo homopolymerization, one first has to synthesize the starting dyad monomer and then polymerize it to obtain the final, alternating copolyester. Otherwise, the copolyester chains will consist of random chain segments consisting of the two monomer units(40,41). 

There is another interesting type of 1 1 alternating copolyester that can be prepared by the reaction given by Equation 1 ... 

In other cases, the number of ions does not reflect the relative abundance of the species, because a "selective suppression" phenomenon is occurring at the sample surface. In such cases, different species are competing for space at the sample surface and some species are able to suppress the presence of others. This phenomenon has been observed, for instance, in the FAB mass spectra of exactly alternating copolyesters, and in the MALDI mass spectra of a mixture containing polyether chains with and without fullerene in the main chain. ... 

Montaudo, G., Scamporrino, E., and Vitalini, D., Synthesis and Structural Characterization of Exactly Alternating Copolyesters Containing Photolabile Units in the Main Chain, Polymer, 30, 297 (1989). 

FAB-MS has been applied also to the characterization of the oligomers present in copolymers, in order to obtain detailed information on the comonomer sequence. For instance, an exactly alternating copolyester (PET/ PETx) containing ethylene terephthalate (PET) and ethylene truxillate (PETx) units... 

The OS-Ar-8 polymer is an alternating copolyester consisting of oxy-l,4-phenyleneoxy-terephthaloyl(PT) and oxy-l,4-phenyleneoxydecanoyl(PD) units. In contrast, the OS-10-8 polymer is a terpolyester having a sequential order of oxy-l,4-phenyleneoxy-terephthaloyl(PT), oxy-l,10-decamethyleneoxyterephthaloyl (PT) and oxy-l,4-phenylene-oxydecanoyl (PD) units. 

In Figure 7.7 shows the results of degradation experiments for synthesised polyesters with a lipase from Pseudomonas sp. The degradation behaviour of the alternating copolyester gives an indication that temperature plays the predominant role in controlling the biodegradation of copolyesters. 

PCTA likewise refers to an acid-modified PCT copolyester. Isophthalic acid (IPA), or alternatively the dimethyl ester of IPA, is the most commonly used modifying dibasic acid to prepare PCTA copolyesters. PCTA thus refers to PCT compositions modified with up to 50 mol% IPA. The PCTA structure is as follows ... 

Aluminum isopropoxide has been used for the preparation of block copolyesters [147, 148]. Tri-block poly(e-CL-b-DXO-e-CL) was prepared by the sequential addition of different monomers to a living polymerization system initiated with aluminum isopropoxide in THF or toluene solution [95]. An alternative route for the preparation of the tri-block copolymer was to react the diblock poly(e-CL-b-DXO) containing an -OH functionality at the chain end using a difunctional coupling agent such as isocyanate or acid chloride (Scheme 18). However, the molecular weights were low and full conversion of monomers was not achieved. 

Preparation and Processing of Selected Polyaxial Copolyesters as Synthetic Alternatives to Surgical... 

Polyaxial copolyesters may be well suited to preparing a synthetic alternative to surgical gut sutures. 

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