Effect of crosslinking rate on the glass transition temperature of polyimide cross-linked silica aerogels

Luo, Zhongyi; Yang, Zichun; Fei, Zhifang; Li, Kunfeng

doi:10.1007/s10965-020-02082-9

Cited by 20 publications

(11 citation statements)

References 21 publications

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“…Besides, the glass transition temperature ( T g ) also has a wide range from 22 to 148 °C (Figure S4, Supporting Information). The segment size and the free radical volume inside polymers affected the glass transition temperature . Smaller molecule chain segment size was easier to move, and the molecule chain segment was more flexible, so the T g of SMPU1 was the lowest.…”

Section: Resultsmentioning

confidence: 99%

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Shape Memory Supramolecular Polyurea with Adjustable Toughness and Ultrahigh Energy Density

Leng

2022

ACS Appl. Polym. Mater.

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As typical stimulus-responsive materials, shape memory polymers (SMPs) have potential for many advanced applications owing to their controllable and programmable shape-changing properties. However, the combination of high toughness and tailorable strength remains a challenge to overcome for SMPs. Here, we engineered meticulously a supramolecular structure with quadruple and double hydrogen bonding arrays to achieve shape memory polyurea elastomers with adjustable strength and toughness. The polyurea with a supramolecular structure had the highest tensile strength of 47 MPa and ultrahigh toughness up to 256 MJ m −3 . Meanwhile, the polyurea was also adjustable to a small tensile strength of 0.87 MPa matching the tensile strength of biological soft tissue (≈1 MPa). The reversible hydrogen bonding arrays endowed polyurea with a shape memory effect as well as excellent selfhealing properties. More importantly, the prestretched polyurea could raise a 500 g weight, which is over 3968 times its own mass, up to 18 mm, because of a high energy density of 75 MJ m −3 , which was higher than the energy density of most SMPs (generally <1 MJ m −3 ).

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Section: Resultsmentioning

confidence: 99%

“…The segment size and the free radical volume inside polymers affected the glass transition temperature. 52 Smaller molecule chain segment size was easier to move, and the molecule chain segment was more flexible, so the T g of SMPU1 was the lowest.…”

Section: Mechanical Properties Of Smpu Elastomersmentioning

confidence: 99%

Shape Memory Supramolecular Polyurea with Adjustable Toughness and Ultrahigh Energy Density

Leng

2022

ACS Appl. Polym. Mater.

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“…Therefore, the local mobility of molecular chains is crucial for gas barrier properties. The higher the local mobility of molecular chains, the easier the gas diffusion [ 29 , 30 ]. Mean square displacement (MSD) in the two PI materials was separately calculated via molecular simulation.…”

Section: Resultsmentioning

confidence: 99%

Impact of Backbone Amide Substitution at the Meta- and Para-Positions on the Gas Barrier Properties of Polyimide

et al. 2021

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This study designed and synthesised a meta-amide-substituted dianiline monomer (m-DABA) as a stereoisomer of DABA, a previously investigated para-amide-substituted dianiline monomer. This new monomer was polymerised with pyromellitic dianhydride (PMDA) to prepare a polyimide film (m-DABPI) in a process similar to that employed in a previous study. The relationship between the substitution positions on the monomer and the gas barrier properties of the polyimide film was investigated via molecular simulation, wide-angle X-ray diffraction (WXRD), and positron annihilation lifetime spectroscopy (PALS) to gain deeper insights into the gas barrier mechanism. The results showed that compared with the para-substituted DABPI, the m-DABPI exhibited better gas barrier properties, with a water vapour transmission rate (WVTR) and an oxygen transmission rate (OTR) as low as 2.8 g·m−2·d−1 and 3.3 cm3·m−2·d−1, respectively. This was because the meta-linked polyimide molecular chains were more tightly packed, leading to a smaller free volume and lower molecular chain mobility. These properties are not conducive to the permeation of small molecules into the film; thus, the gas barrier properties were improved. The findings have significant implications for the structural design of high-barrier materials and could promote the development of flexible display technology.

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“…To overcome this issue, natural alternatives such as tannic acid, genipin, citric acid and ferulic acid are utilized as crosslinkers [19] . Through the process of crosslinking, the mechanical stability is improved while swelling, elasticity and drug release properties of the hydrogel are altered [20] …”

Section: Introductionmentioning

confidence: 99%

“…[19] Through the process of crosslinking, the mechanical stability is improved while swelling, elasticity and drug release properties of the hydrogel are altered. [20] Tannic acid (TA) is a natural, biocompatible molecule that is composed of a glucose molecule esterified at all five hydroxyl functional groups by gallic acid molecules, which themselves bind to five other gallic acid molecules through ester bonds. [21] TA is regarded to be safe by the FDA for the treatment of skin ulcers, burns and lowering of blood pressure.…”

Section: Introductionmentioning

confidence: 99%

In Vitro Release Kinetics of Nystatin and Tannic Acid in Artificial Body Fluids from Hydrogels Prepared by Using Polyvinylpyrrolidone Crosslinked with Tannic Acid

Patel,

Lata,

Sharma

et al. 2023

ChemistrySelect

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Biocompatible hydrogels of polyvinylpyrrolidone (PVP) with tannic acid (TA) in the weight ratios of 1 : 0.70 (70 %)–1 : 0.60 (60 %) were prepared and loaded with the antifungal drug, nystatin (NYS). The hydrogel is expected to exhibit a two‐fold (anti‐bacterial and anti‐fungal) characteristics. Infrared spectroscopy (IR), viscometry and differential scanning calorimetry (DSC) were used to investigate interactions between PVP and TA. In vitro release kinetics of NYS in simulated body fluid (SBF) and sweat (SS) were studied using ultra‐violet spectroscopy (UV) and high‐performance liquid chromatography (HPLC). An increase in the glass transition temperature (Tg) of PVP accompanied with changes observed in the OH stretching, C=O and the C−O−C regions in the IR spectrum in dried PVP/TA hydrogel suggested physical crosslinking. The swelling of the hydrogels in distilled deionized water (DDW), SBF and SS decreased with increasing TA concentration and showed pH sensitivity. TA release followed the Korsmeyer‐Peppas kinetic model regardless of swelling media while NYS followed the Korsmeyer‐Peppas and Hixson‐Crowell cube root law in SS and SBF respectively. TA was active against Escherichia coli and Staphylococcus aureus while NYS against Candida albicans. A topical patch was prepared by adhering the drug loaded PVP/TA hydrogel onto silicone strips.

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Effect of crosslinking rate on the glass transition temperature of polyimide cross-linked silica aerogels

Cited by 20 publications

References 21 publications

Shape Memory Supramolecular Polyurea with Adjustable Toughness and Ultrahigh Energy Density

Shape Memory Supramolecular Polyurea with Adjustable Toughness and Ultrahigh Energy Density

Impact of Backbone Amide Substitution at the Meta- and Para-Positions on the Gas Barrier Properties of Polyimide

In Vitro Release Kinetics of Nystatin and Tannic Acid in Artificial Body Fluids from Hydrogels Prepared by Using Polyvinylpyrrolidone Crosslinked with Tannic Acid

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