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Characterisation of the Fundamental Interactions Between Water and Cellulose Ether Polymers.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Characterisation of the Fundamental Interactions Between Water and Cellulose Ether Polymers./
作者:	McCrystal, Conor B.
面頁冊數:	1 online resource (344 pages)
附註:	Source: Dissertations Abstracts International, Volume: 70-12, Section: B.
Contained By:	Dissertations Abstracts International70-12B.
標題:	Cellulose acetate. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=U483431click for full text (PQDT)
ISBN:	9798582548805

Characterisation of the Fundamental Interactions Between Water and Cellulose Ether Polymers.
McCrystal, Conor B.

Characterisation of the Fundamental Interactions Between Water and Cellulose Ether Polymers. - 1 online resource (344 pages)

Source: Dissertations Abstracts International, Volume: 70-12, Section: B.

Thesis (Ph.D.)--Liverpool John Moores University (United Kingdom), 1998.

Includes bibliographical references

The thesis characterises the behaviour of water in gels of cellulose ether polymers that are commonly used in hydrophilic matrix systems. Detailed studies on the hydrated polymer which forms a gel and more specifically on the types of water which exist within this gel are fundamental in the optimisation of cellulose ethers for their applications in sustained release formulations.Characteristic thermal events were apparent in the DSC scans of HPMC K15M gels, which were dependent on gel hydration time, polymer concentration and the cooling and heating rates utilised during scanning. These events were related to the presence of different types of water in HPMC K15M gels; free water, the main endothermic peak at around 0°C, bound water and loosely bound water, giving rise to smaller peaks prior to the main peak at temperatures from -15 to 0°C. These pre-endothermic events were unaffected when gel samples were cooled to -50°C, heated to -9°C and subsequently recooled and reheated to +35°C. Upon cooling to -50°C, heating to -9°C and holding for 10mins, and then recooling and reheating again, their occurrence and the temperature at which they appeared remained unaffected. Therefore it was concluded that these pre-endothermic events were real and they were reproducible. TGA and dielectric spectroscopy studies also provided evidence for the existence of more than one type of water within HPMC K15M gels. Water evaporating in more than one event was visible from the first derivative of the TGA weight loss curve, which was dependent on polymer concentration and scanning rates. The behaviour of water in HPMC K15M gels was characterised using low frequency dielectric spectroscopy from -30 to +22°C. The shape of the dielectric response curves showed that in addition to the melting of free water, a number of other processes were occurring indicating that the melting of different types of water prior to the melting of free water. These processes were dependent on polymer concentration and the results were in agreement with the DSC findings, confirming the presence of different types of water in these gel systems.The amount of water bound per PRU in HPMC K15M gels were calculated using DSC results based on methods previously reported. The characteristic events visible in both DSC and LFDS studies were dependent on polymer molecular weight, substitution type and hydration time. The BW per PRU for cellulose ethers after 96h hydration were; HPMCs K100LV (4.4), K4M (4.5), K15M (6.5), K100M (6.6), E4M (5.6), F4M (5.4), MC A4M (3.8) and HPC (6.1). The distinctive events visible in both DSC and LFDS studies and the separation of evaporation events in TGA were influenced by the addition of a drug. Propranolol hydrochloride (water-soluble) reduced the amount of water bound to the majority of polymers, the so called 'salting-in' effect. However, more water was required to fully hydrate the majority of polymers in the presence of diclofenac sodium (poorly water-soluble) in comparison with the effects seen in the presence of propranolol hydrochloride, the so called 'salting-out' effect.Polymer molecular weight had little effect on their moisture sorption/desorption characteristics in comparison to polymer substitution type which appeared to have an effect on these properties. HPMC K4M sorbed more moisture at all RH values and had a larger hysteresis area compared to that for HPMCs E4M, F4M and MC A4M.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798582548805Subjects--Topical Terms:

3695528
Cellulose acetate.
Subjects--Index Terms:

Hydrated polymersIndex Terms--Genre/Form:

542853
Electronic books.

Characterisation of the Fundamental Interactions Between Water and Cellulose Ether Polymers.
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245 1 0 $a Characterisation of the Fundamental Interactions Between Water and Cellulose Ether Polymers.
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500 $a Source: Dissertations Abstracts International, Volume: 70-12, Section: B.
500 $a Advisor: Rajabi-Siahboomi, Ali R.; Ford, James.
502 $a Thesis (Ph.D.)--Liverpool John Moores University (United Kingdom), 1998.
504 $a Includes bibliographical references
520 $a The thesis characterises the behaviour of water in gels of cellulose ether polymers that are commonly used in hydrophilic matrix systems. Detailed studies on the hydrated polymer which forms a gel and more specifically on the types of water which exist within this gel are fundamental in the optimisation of cellulose ethers for their applications in sustained release formulations.Characteristic thermal events were apparent in the DSC scans of HPMC K15M gels, which were dependent on gel hydration time, polymer concentration and the cooling and heating rates utilised during scanning. These events were related to the presence of different types of water in HPMC K15M gels; free water, the main endothermic peak at around 0°C, bound water and loosely bound water, giving rise to smaller peaks prior to the main peak at temperatures from -15 to 0°C. These pre-endothermic events were unaffected when gel samples were cooled to -50°C, heated to -9°C and subsequently recooled and reheated to +35°C. Upon cooling to -50°C, heating to -9°C and holding for 10mins, and then recooling and reheating again, their occurrence and the temperature at which they appeared remained unaffected. Therefore it was concluded that these pre-endothermic events were real and they were reproducible. TGA and dielectric spectroscopy studies also provided evidence for the existence of more than one type of water within HPMC K15M gels. Water evaporating in more than one event was visible from the first derivative of the TGA weight loss curve, which was dependent on polymer concentration and scanning rates. The behaviour of water in HPMC K15M gels was characterised using low frequency dielectric spectroscopy from -30 to +22°C. The shape of the dielectric response curves showed that in addition to the melting of free water, a number of other processes were occurring indicating that the melting of different types of water prior to the melting of free water. These processes were dependent on polymer concentration and the results were in agreement with the DSC findings, confirming the presence of different types of water in these gel systems.The amount of water bound per PRU in HPMC K15M gels were calculated using DSC results based on methods previously reported. The characteristic events visible in both DSC and LFDS studies were dependent on polymer molecular weight, substitution type and hydration time. The BW per PRU for cellulose ethers after 96h hydration were; HPMCs K100LV (4.4), K4M (4.5), K15M (6.5), K100M (6.6), E4M (5.6), F4M (5.4), MC A4M (3.8) and HPC (6.1). The distinctive events visible in both DSC and LFDS studies and the separation of evaporation events in TGA were influenced by the addition of a drug. Propranolol hydrochloride (water-soluble) reduced the amount of water bound to the majority of polymers, the so called 'salting-in' effect. However, more water was required to fully hydrate the majority of polymers in the presence of diclofenac sodium (poorly water-soluble) in comparison with the effects seen in the presence of propranolol hydrochloride, the so called 'salting-out' effect.Polymer molecular weight had little effect on their moisture sorption/desorption characteristics in comparison to polymer substitution type which appeared to have an effect on these properties. HPMC K4M sorbed more moisture at all RH values and had a larger hysteresis area compared to that for HPMCs E4M, F4M and MC A4M.
533 $a Electronic reproduction. $b Ann Arbor, Mich. : $c ProQuest, $d 2023
538 $a Mode of access: World Wide Web
650 4 $a Cellulose acetate. $3 3695528
650 4 $a Polymers. $3 535398
650 4 $a Molecular weight. $3 3683783
650 4 $a Viscosity. $3 1050706
650 4 $a Pharmaceutical sciences. $3 3173021
650 4 $a Rheology. $3 570780
653 $a Hydrated polymers
653 $a Sustained release
653 $a Cellulose ethers
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