Polyesters general structures

Polycarbonate is a polyester in which dihydric (or polyhydric) phenols are joined through carbonate linkages. The general-purpose type of polycarbonate is based on 2,2-bis(4 -hydroxybenzene)propane (bisphenol A) and has the general structure ... 

The COOH group at one end of the ester molecule can react with another alcohol molecule. The OH group at the other end can react with an acid molecule. This process can continue, leading eventually to a long-chain polymer containing 500 or more ester groups. The general structure of the polyester can be represented as... 

Polycarbonates. Linear thermoplastic polyesters of carbonic acid with aliphatic or aromatic di-hvdroxv compds. A general structure presentation is as follows (Ref 4) ... 

For those familiar with polymer chemistry, polyurethane may be a confusing term. Unlike polyethylene, the polymerization product of ethylene, a polyurethane is not the result of the polymerization of urethane. To add to the confusion, a urethane is a specific chemical bond that comprises a very small percentage of the bonds of a polyurethane. Since we are interested in chemical and physical effects, polyether or polyester is a more descriptive term for the most common bond in a polyurethane. Despite this complication, it is instructive to begin by talking about the methane bond from which the polyurethane name is derived. The general structure or bond that forms the basis of this chemistry is the urethane linkage shown in Figure 2.1. 

Polyesters are known to be produced by many bacteria as intracellular reserve materials for use as a food source during periods of environmental stress. They have received a great deal of attention since the 1970s because they are biodegradable, can be processed as plastic materials, are produced from renewable resources, and can be produced by many bacteria in a range of compositions. The thermoplastic polymers have properties that vary from soft elastomers to rigid britde plastics in accordance with the structure of the pendent side-chain of the polyester. The general structure of this class of compounds is shown by (3), where R = -(-CH2-) CH3, n = > 100, and m = 0 8. 

There are a class of polyesters that have the general structure ... 

Iwata el al. report a novel photocrosslinkable polyester of p-phenylene-bis-(a-cyanobutadiene carboxylic acid) of the general structure (4). The photosensitivity of this polymer is high enough even for the effective use of a weak... 

Polymers of e-caprolactone, a biodegradable polyester with many similarities to the pLA/pGA family, are also useful in drug delivery [5]. The general structure of poly(c-caprolactone) is ... 

The above-described behavior is well accepted and is considered a general one, although there are some interesting exceptions. For example, within the homologous series of polyesters with the general structure [126] given by 10, and marked CmCn,... 

The first commercial thermoplastic elastomers (TPE) were the thermoplastic urethanes (TPU). Their general structure is A-B-A-B, where A represents a hard crystalline block derived by chain extension of a diisocyanate with a glycol. The soft block is represented by B and can be derived from either a polyester or a polyether. Figure 5.1 shows typical TPU structures, both polyester and polyether types. 

Molecules of product continue to react with available monomers until, finally, a polyester is formed with the general structure given above, where the n means that the unit in parentheses is repeated many times. 

Based on these functionalities, linkage groups can be added to the polyester for carrying active compounds [25]. The general structure of PHA and its follow-up products after postsynthetic modification are provided in Figure 7.2. 

Figure 7.2 Chemical structures of biobased polyesters, (a) General structure of PHA (b) example of a functional PHA harbouring 5-Phenylvaleryl-, Cyclohexylbutyryl-, 4-Pentenoyl-, 9-Cyanononanoyl-, 5-Methylhexanoyl-, and 8-Bromooctanoyl groups (c) PHA after post-synthetic functionalization (d) PHA with linker group (e) functional PHA active against biofouling [25]. Chiral centres exist at the central carbon atoms indicated by a, b and d-i c indicates the non-chiral center of 4HB 126],...

Many bacteria are a potential source of naturally occurring polyesters, mainly poly(p-hydroxy alkanoate)s, with general structure... 

The general structures in PBT are broadly similar to those in PET and have been discussed earlier, with the exception of four methylene groups in the aliphatic portion of the polyester chain. Assuming, as is plausible, that the degradation route undergone by PET will apply to PBT, the chain scission via 3-hydrogen transfer through a six-membered cyclic intermediate will proceed as ... 

Almost a mirror image of poly(alkylene terephthalate)s (PAT), these polymers are essentially polyesters formed from aliphatic diacids and hydroquinone (1,4-dihydroxybenzene), giving the general structure ... 

Allied Signal Incorporated [87] have patented cinnamamides of the general structure Ph[NH-(C=0)-C(CN)=CPh2]2, and have observed that these are especially effective stabilisers for aromatic polyesters. Clariant have noted that a combination of benzylidene bis-malonates with hindered amine light stabilisers showed excellent synergism in UV-stabilising polyalkylene terephthalates [88]. 

The ability of a polymeric material to crystallise is determined by its molecular structure, that is its structural regularity and flexibility. A regular structure has the potential to exhibit crystallinity, while an irregular structure will tend to be amorphous. The general structure of polyester resin is very complex as these resins are obtained from a mixture of fatty acids with different structures and compositions. In addition, no stereo-specific catalyst is used in the resinification reaction, so the product obtained is random in nature. Thus crystallinity in polyester resins is rarely obtained, most being rather amorphous and highly flexible. 

Dielectric and dynamic mechanical data for poly(ethylene terephthalate) (PET) (Tm 538 K), poly(butylene tereph-thalate) (PBT) (Tn, 493 K), and several fully aromatic polyesters or polyarylates having the general structure shown below... 

Alkyl phosphonates with a general structure of RP(=0)(0R )(0R ). They are generally viscous Uquids with applications in rigid PUR, highly filled polyesters, and PET fibers. 

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