Polyanhydrides thermal properties

B. Characterization of Thermal Properties, Crystallinity, and Phase Behavior of Polyanhydrides... 

It is important to characterize the thermal properties of polyanhydrides that are proposed for drug delivery applications, as changes in crystallinity... 

Polyanhydrides are a class of bioerodible polymers that have shown excellent characteristics as drug delivery carriers. The properties of these biomaterials can be tailored to obtain desirable controlled release characteristics. Extensive research in this promising area of biomaterials is the focus of this entry. In the first part of the entry, the chemical structures and synthesis methods of various polyanhydrides are discussed. This is followed by a discussion of the physical, chemical, and thermal properties of polyanhydrides and their effect on the degradation mechanism of these materials. Finally, a description of drug release applications from polyanhydride systems is presented, highlighting their potential in biomedical applications. 

To understand the properties that make polyanhy-drides suitable drug carriers, their chemical, physical, and thermal behavior need to be characterized. This section discusses the methods to determine the chemical structure and composition, the molecular weight, the thermal properties, the phase behavior, the stability, and the erosion mechanism of polyanhydrides. 

In the past decade, extensive research has been carried out on the characterization of polyanhydrides. This section will describe the methods used for the characterization of polyanhydrides and data obtained about their chemical composition and structure, crystallinity and thermal properties, mechanical properties, and thermodynamic and hydrolytic stability. 

In addition, polyanhydrides have been shown to have excellent in vivo biocompatibility [57]. The thermal properties of representative P(CPP-co-SA) copolymers are given in Table 55.1. A detailed presentation of thermal properties is given in Domb et al. and Tamada and Langer [48,58]. 

Polyanhydrides have been characterized with regard to their chemical composition, structure, crystallinity and thermal properties, mechanical properties, thermodynamic properties, and hydrols c stability A representative set of analysis data has been summarized for the polyanhydrides poly(EAD-SA) and poly(CPP-SA) (Table 4). H NMR spectroscopy indicates the degree of randomness that suggests whether the polyanhydrides is either a random or a block copolymer the average length of sequence (Ln) and the frequency of occurrence of specific comonomers sequences (58). The anhydride bond presents characteristic peaks in... 

Anastasiou, T.J. Uhrich, K.E. Novel polyanhydrides with enhanced thermal and solubility properties. Macromolecules 2000, 33 (17), 6217-6221. 

In the 1930 s, Carothers prepared a series of aliphatic poly(anhydride)s for potential use as fibers in the textile industry (1). However, the hydrolytic stability of these materials was very poor. By the mid-1950 s, Conix was able to synthesize aromatic poly(anhydride)s with improved film and fiber forming properties (2). Despite these properties, the polyanhydrides poor thermal and hydrolytic stability resulted in their limited use, and no conunercial applications were found. By the late 1960 s, however, hydrolytic instability became an important factor for polymers utilized in the manufacture of medical devices such as absorbable sutures and drug delivery systems. 

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