Aligned-porous-structured poly(vinyl alcohol) foams with cellulose nanocrystals

Abstract

Poly(vinyl alcohol) (PVA) foams were prepared using a green lyophilization process without the use of foaming agents. PVA solutions with contents of CNCs (1-4 wt%) were prepared at two different freezing temperatures (-20 and-186 °C). With the addition of CNCs, moisture uptake of the CNC-PVA foams prepared at two freezing temperatures was lower than the neat PVA foams. With increasing CNC contents, no significant change of the moisture uptake could be observed for both types of the foams. Similar values of the moisture uptake could be found from both foams frozen at-20 and-186 °C. Scanning electron microscope measurements revealed the aligned-porous-structure of the foams frozen at-186 °C along with the ice growth direction while large and elongated pores were observed from the foams with the lower freezing temperature. These unique features of the foams prepared by a freeze-drying technique could be controlled by changing the freezing temperature, and these foams could be useful for specific applications such as tissue engineering scaffolds, thermal insulators or filters.

Recent development of plant-derived nanocellulose in polymer nanocomposite foams and multifunctional applications: A mini-review

“…Foam is generally prepared by dispersing gases into a liquid, solid or hydrogel using various approaches such as freeze-drying, supercritical drying, oven drying and melt-processing, and porous foam materials have a wide range of applications such as packaging, absorption and tissue engineering owing to light weight, low density and heat and sound insulation [40,[46][47][48]. Due to superior mechanical performances and size in the nanoscale, nanocellulose has attracted more attention as reinforcement to improve mechanical properties of petroleum and bio-based polymer foams such as polyurethane (PU), poly(vinyl alcohol) (PVA), poly(lactic acid) (PLA), tannin and xylan [48][49][50][51][52][53][54][55][56][57][58][59][60][61]. Mechanical properties of foams depend on cell structure (close and open cell) and cell wall properties.…”

Recent Progress in Cellulose Nanocrystal Alignment and Its Applications

“…Aligned porous-structured foams with CNCs at two different freezing temperatures were developed. 186 The addition of CNCs into a poly(vinyl alcohol) foam reduced the moisture uptake. At −186 °C, a highly aligned porous foam structure was observed along the direction of ice growth.…”

“…This could be a potential application for biosensors that work on the principle of external stimuli. Aligned porous-structured foams with CNCs at two different freezing temperatures were developed . The addition of CNCs into a poly­(vinyl alcohol) foam reduced the moisture uptake.…”

Cellulose Nanomaterials as a Future, Sustainable and Renewable Material

“…Figure 3. (A) AFM images of CNs deposited on mica and (B) TEM images of modified NC on the copper grid (reproduced with permission from author[36,37]). …”