当前位置: X-MOL 学术Biomacromolecules › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Swelling and Free-Volume Characteristics of TEMPO-Oxidized Cellulose Nanofibril Films
Biomacromolecules ( IF 5.5 ) Pub Date : 2018-02-08 00:00:00 , DOI: 10.1021/acs.biomac.7b01814
Jonathan Ø. Torstensen 1 , Ming Liu 2 , Soo-Ah Jin 3 , Liyuan Deng 1 , Ayman I. Hawari 2 , Kristin Syverud 1, 4 , Richard J. Spontak 3, 5 , Øyvind W. Gregersen 1
Affiliation  

Cellulose nanofibrils (CNFs) are becoming increasingly ubiquitous in diverse technologies requiring sustainable nanoscale species to form or modify films. The objective of the present study is to investigate the swelling behavior and accompanying free volume of self-standing TEMPO-oxidized (TO) CNF films in the presence of water vapor. For this purpose, we have performed time-resolved swelling experiments on films, prepared according to different experimental protocols, at 90% relative humidity (RH) and ambient temperature. Corresponding free-volume characteristics are elucidated by positron annihilation lifetime spectroscopy (PALS) conducted at ambient temperature and several RH levels. Increasing the drying temperature of the films (from ambient to 50 °C) is observed to promote an increase in film density, which serves to reduce bulk swelling. These elevated drying temperatures likewise cause the free-volume pore size measured by PALS to decrease, while the corresponding total free-volume fraction remains nearly constant. Similarly, dispersion of TO-CNF into aqueous suspensions by ultrasonication prior to film formation increases both the total free-volume fraction and pore size but reduces the size of individual nanofibrils with little net change in bulk swelling. The swelling and concurrent free-volume measurements reported here generally reveal an increase in the free volume of TO-CNF films with increasing RH.

中文翻译:

TEMPO氧化纤维素纳米原纤维薄膜的溶胀和自由体积特性

纤维素纳米纤丝(CNF)在要求可持续的纳米级物种形成或修饰薄膜的各种技术中变得越来越普遍。本研究的目的是研究在水蒸气存在下自支撑的TEMPO氧化(TO)CNF薄膜的溶胀行为和随之产生的自由体积。为此,我们在90%相对湿度(RH)和环境温度下对根据不同实验方案制备的薄膜进行了时间分辨的溶胀实验。通过在环境温度和几个RH水平下进行的正电子an没寿命光谱(PALS)阐明了相应的自由体积特性。观察到膜的干燥温度升高(从环境温度到50°C)可促进膜密度的增加,从而减少整体溶胀。这些升高的干燥温度同样导致通过PALS测量的自由体积孔径减小,而相应的总自由体积分数几乎保持恒定。类似地,在成膜之前通过超声将TO-CNF分散到水性悬浮液中会增加总自由体积分数和孔径,但会减小单个纳米原纤维的大小,而体积溶胀的净变化很小。此处报道的溶胀和同时发生的自由体积测量通常显示出,随着RH的增加,TO-CNF薄膜的自由体积会增加。在成膜之前通过超声将TO-CNF分散到水悬浮液中会增加总自由体积分数和孔径,但会减小单个纳米原纤维的大小,而体积溶胀却几乎没有净变化。此处报道的溶胀和同时发生的自由体积测量通常显示出,随着RH的增加,TO-CNF薄膜的自由体积会增加。在成膜之前通过超声将TO-CNF分散到水悬浮液中会增加总自由体积分数和孔径,但会减小单个纳米原纤维的大小,而体积溶胀的净变化很小。此处报道的溶胀和同时发生的自由体积测量通常显示出,随着RH的增加,TO-CNF薄膜的自由体积会增加。
更新日期:2018-02-08
down
wechat
bug