Physical and Chemical Modifications

Heat-water treatment involves exposing starch with low moisture content (18%-27%) to high temperature. Heat-water treatment physieally modifies the starch. The low moisture content limits molecnlar mobility and gelatinization during treatment. Starch that has been heat-water treated has increased gelatinization temperature. 

---

The synthesis of new polymeric materials having complex properties has recently become of great practical importance to polymer chemistry and technology. The synthesis of new materials can be prepared by either their monomers or modification of used polymers in industry. Today, polystyrene (PS), which is widely used in industrial applications as polyolefins and polyvinylchlorides, is also used for the production of plastic materials, which are used instead of metals in technology. For this reason, it is important to synthesize different PS plastic materials. Among the modification of PS, two methods can be considered, viz. physical and chemical modifications. These methods are extensively used to increase physico-mechanical properties, such as resistance to strike, air, or temperature for the synthesizing of new PS plastic materials. 

Sometimes the enzyme immobilization may involve both physical and chemical modifications of the protein ( hybrid techniques ). 

Cell Colonization Control by Physical and Chemical Modification of Materials... 

What physical and chemical modifications of the lead compound have the best potential to improve its properties in the desired directions Ay The modified properties can be written as y + Ay, and the modified structure can be written as X + Ax. The derivative Ax/Ay represents the structure change required to achieve a particular property change. 

Photochemical and photophysical processes in cellulose and related compounds have received considerable attention during the last decades, resulting in research work concerned with the improvement of cellulosic materials via physical and chemical modifications. One method was to apply a copolymer between the cellulose and a synthetic polymer which are generally grafted by free radical reactions. 

This review has shown that most studies on barley starches have been focused on understanding the fine structures, particle size distribution, chemical composition, gelatinization properties and susceptibility towards enzyme hydrolysis. However, there is a dearth of information on the rheological and retrogradation characteristics of barley starches from different cultivars. Furthermore, the response of small and large barley starch granules towards physical and chemical modification needs investigation. Research in the above areas is underway in our laboratories. It is hoped that this study may improve the utilization of different types of barley starches for specific products within the food and paper industry. 

Boudreau, A., Arul, J. 1991. Physical and chemical modification of milk fat. 2.1 Fractionation. In, Monograph on Utilizations of Milk fat, Bulletin, No. 260, International Dairy Federation, Brussels, pp. 7-15. 

Combination of Physical and Chemical Modification of Modern Paper. The photostabilization of modern paper can be further improved by combination of the above-mentioned two systems. The addition of stabilizers to chemically modified modern paper can avoid further photo-induced reactions through the incomplete elimination of the chromophoric moiety in the paper. 

In what follows, a number of methods developed by our group to prepare toughened polymeric composites, which involve both physical and chemical modifications and are based on the concentrated emulsion pathway, are presented [27-29]. 

Many suitable methods for physical and chemical modification of the drug absorbance have been reported. For exmnple, the bathochromic effect is used in the difference spectrophotomehic assay of barbiturates. The absorbance of the sample at about pH 10 where the mono-anionic species... 

Oshima, T., Sato, K., Terauchi, M., and Sato, M. 1997. Physical and chemical modifications of high-voltage pulse sterilization. Journal of Electrostatics 42 159-166. 

However, research on carbon nanotubes has opened new avenues in the area of materials science and carbon surface derivatization. Their physical and chemical modifications offer excellent opportunities not only in the characterization and understanding of CNT chemistry, but also in highlighting their potential applications. In the context of this chapter, one important application of CNTs is their use as support for homogeneous catalysts in fact, based on the very few examples published in the literature, this is clearly a very promising area. Furthermore, the potential extrapolation of the CNT derivatization methodologies to more traditional and other recent carbon materials (mesoporous and ordered porous carbon materials) is also one of the major challenges for all researchers who are involved with carbon materials. 

Parkhouse RME, Dutton RW (1967) The effect of physical and chemical modifications on antigen in the secondary response in vitro. Immunochemistry 4 431-439... 

The investigation of the polymer modifications induced by the oxygen ion beam must be started by considering the specific structural features of the untreated polymer. Only after this, both physical and chemical modifications produced by the ion beam can be considered. Moreover, their dependence on beam energy and dose should also be considered. 

The electrons in low-temperatnre plasmas are able to cleave covalent chemical bonds, thereby prodncing physical and chemical modifications of the snrface of the treated substrate withont changing the fiber properties. 

In previous papers(i-.3), we have reported that a specially prepared poly(vinyl alcohol) (PVA) film is very low in protein adsorption and platelet adhesion compared with conventional PVA and other polymers. When PVA is used for practical applications as non aqueous solutions, physical or chemical crosslinking or acetalization is introduced to PVA to make it insoluble in water. Acetalization with formaldehyde and physical crosslinking by heat treatment (annealing) are the most common among the insolubilization methods(. However, for the minimum protein adsorption and platelet adhesion, these physical and chemical modifications have to be avoided because significant interactions with biological components are observed for such PVA, similar to the conventional polymers. 

Among them, PHA, PLA and PBS are well known for their biodegradabiUty, whereas PE, PTT and PPP are probably less biodegradable or are less studied in terms of their biodegradability. Over the past years, their properties and applications have been studied in detail and products have been developed. Physical and chemical modifications to reduce their cost or to improve their properties have been conducted. 

Physical and chemical modifications of clays have been used for the production of materials for practical applications. The properties of clay can also be modified by adsorption and intercalation of organic polymers. The pillarization is a modification method that usually involves the intercalation of cationic species acting as pillars to support the mineral layers, separating them, creating a porous material useful for adsorption of organic compounds and other environmental applications (Bergaya et al., 2006). 

The only area in which wood-related materials is witnessing important research contributions, concerns its physical and chemical modification, in order to protect it against degradation by various reagents or to obtain novel properties such as a thermoplastic behaviour. These aspects are treated in Chapter 20. 

Physical and chemical modifications to increase electrospun polyester hydrophihcity and surface scaffold functionalization with ECM proteins, peptides, or other bioactive molecules are some examples of posttreatments in use [16]. Another strategy to improve the biocompatibihty of the scaffolds is to combine the polyester with a natural polymer or other natural biomolecule to conduct the electrospinning process [17,18]. 

Pignataro, B., Licciardello, A., Cataldo, S., Marietta, G. (2003) SPM and ToF-SIMS investigation of the physical and chemical modification induced by tip writing of self-assembled monolayers. Mater. Sci. Eng. C, 23, 7-12. 

Polymeric materials offer the practitioner a wide range of potential products that can be utilized effectively to meet the pressing needs of modem technology. The possibilities of physical and chemical modifications, as well as of copolymerization, mean that a polymer can literally be tailor-made for given end uses. 

Modification of chitosan is to introduce special properties into these abnndant biopolymers and enlarge their fields of potential apphcations (Hong-Mei Kang et al., 2006). Physical and chemical modifications have been performed for improving metal sorption selectivity by template formation (or) the imprinting method (Baba et al., 1998 Cao et al., 2001 Tan et al., 2001). 

Zi ba T, Kapelko M, Gryszkin A. Selected properties of potato starch subjected to multiple physical and chemical modifications. Pohsh J Food Nutr Sci 2007 57 (4) 639-645. 

---