14 research outputs found
In-depth study of the interaction mechanism of lignin molecules
Department of Chemical Engineeringclos
Analysis of intermolecular binding forces between lignin nanofilms in electrolyte solutions
Understanding the molecular mechanism of lignin adhesion using self-assembled monolayers
In-Depth Study of the Interaction Mechanism between the Lignin Nanofilms: Toward a Renewable and Organic Solvent-Free Binder
Lignin is an abundant biorenewable resource with an annual production of 50 million metric tons. Despite the abundance and high potential for applications, only ???2% of the produced lignin was used for industrial applications. One of the main reasons for the low applicability is the lack of fundamental studies. In particular, the molecular binding mechanism of lignin is a key for the development and design of lignin into higher-value products. In this study, the interaction forces between homogeneous lignin nanofilms as thin as a phenylpropane unit monolayer (???11 ??) are directly measured using a surface forces apparatus (SFA) at various concentrations of intervening electrolyte solution. The measured adhesion force decreases with increasing electrolyte concentration, the inverse of what would be expected according to the electric double layer theory. These findings, along with detailed analyses using Derjaguin???Landau???Verwey???Overbeek (DLVO) and hydrophobic theories, strongly indicate that hydrophobic interaction accounts for a large proportion of the interaction forces. Additional measurements between methyl-terminated self-assembled monolayer and lignin film confirm that hydrophobic interactions dominated the overall interaction potential of lignin films. Furthermore, lignin-supplemented activated carbon composites show enhanced compressive strength, which indicates the potential use of lignin as an ecofriendly reinforcing binder
What construction topics do they discuss in social media? : a case study of Weibo in China
As a traditional industry such as the construction, it is hard to collect data for management and improvement. Traditional ways such as questionnaire survey, interviews, or focus meetings to collect data are both time- and cost-consuming. Recently, with the rapid development of social media services, data can be collected and extracted for topic analysis to provide officials and managers with fresh perspectives on participants in the construction management. In this paper, a topic analysis systematic framework is proposed. This system collected user messages from social media sites, establishes and compares different clusters’ topics and keywords in their messages. This paper generated valuable information and knowledge in the construction domain. As an initial trial, this study selected social media of Weibo because of its wide usage in China. Four clusters which include construction workers, construction companies, construction unions, and construction media were analyzed. For each user, the crawler is used to collect the Weibo messages from his/her web page. On average, there are 135 messages collected for each user. This research then analyzed these data in the following aspects to dig out information behind data: keywords, hashtags, and topic modeling. Detailed findings, benefits, and barriers to incorporating social media data analytics in the construction industry, along with future research, were discussed. This paper benefits the academia by testing an alternative way of studying the construction population, which further will help decision makers better understand the real situations of the construction industry
Sentiment analysis for the construction industry : a case study of Weibo in China
Construction industry is a labor-intensive industry. Sentiment or mood of participants in the construction industry is a key issue in this business. To analyze this issue, using traditional ways such as questionnaire survey to collect data is both time- and cost-consuming. Recently, with the rapid development of social media services, data can be collected and extracted for sentiment analysis to provide officials and managers with fresh perspectives on participants in the construction management. In this paper, a sentiment analysis systematic framework is proposed. This system collected user messages from social media sites, establishes and compare different clusters emotion dictionaries by time duration and location. This paper generated valuable information and knowledge in the construction domain. As an initial trial, this study selected social media of Weibo because of its wide usage in China. Four clusters which include construction workers, construction companies, construction unions, and construction media were analyzed. For each user, the crawler is used to collect the Weibo messages from his/her Web page. On average, there are 135 messages collected for each user. This research then analyzed these data in the following aspects to dig out sentiments behind data: hourly, daily, monthly, and locations. Detailed findings, benefits and barriers to incorporating social media data analytics in the construction industry, along with future research, were discussed. This paper benefits the academia by testing an alternative way of studying the construction population, which further will help decision makers better understand the real situations of the construction industry
Adaptive amphiphilic interaction mechanism of hydroxypropyl methylcellulose in water
Hydroxypropyl methylcellulose (HPMC), an FDA-approved water-soluble cellulose derivative, has been used in various wet-adhesion applications in construction products, paints, and drug delivery for 70 years. Despite the various applications, its adhesion mechanism in water has not been elucidated. Here, we measure the adhesion characteristics of HPMC against itself, hydrophilic and hydrophobic surfaces as a function of temperature using a surface forces apparatus (SFA) in water. The results show that HPMC adheres strongly to all tested surfaces, regardless of hydrophobicity. The adhesive strength of HPMC increases with temperature because of entropydriven hydrophobic interactions and is comparable to or exceeds the wet-adhesion strength of most biological adhesives, including those of mussels and cephalopods. In addition, the elevated temperature induces swelling in HPMC layer, resulting in the exposure of more hydrogen bonding sites, thereby increasing adhesion with the hydrophilic surface. The bulk compression test of the HPMC-silica composite material is consistent with the SFA data and indicates that the water content and temperature are critical variables for the adhesion of HPMC to inorganic surfaces regardless of hydrophobicity. Because adhesive and coating technologies have shifted toward environmentally-friendly systems, these results provide a basis for the fabrication of organic solvent-free HPMCbased composites for future applications
Probing pH-dependent lignin interaction mechanism using a Surface Forces Apparatus (SFA)
pH-dependent interaction mechanism of lignin nanofilms
Lignin has been spotlighted as an abundant renewable bioresource for use in material technologies and applications such as biofuels, binders, composites, and nanomaterials for drug delivery. However, owing to its complex and irregular structure, it is difficult to investigate its fundamental interaction mechanism, which is necessary to promote its use. In this study, a surface forces apparatus (SFA) was used to investigate the pH-dependent molecular interactions between a lignin nanofilm and five functionalized self-assembled monolayers (SAMs). The lignin nanofilm adhered most strongly to the amine-functionalized SAM, indicating that the molecular interactions with lignin were mainly electrostatic and cation????? interactions. The force???distance profile between lignin and a methyl-functionalized SAM revealed pH-dependent interactions similar to those between two lignin nanofilms. This finding indicates that the dominant cohesion mechanism is hydrophobic interactions. A quartz crystal microbalance with dissipation was used to investigate the adsorption of free lignin molecules on functionalized SAMs. Lignin molecules, which were free in solution, were most effectively adsorbed to the phenyl-functionalized SAM. To investigate whether the nanoscopic interaction forces could be extended to macroscopic properties, the compressive strength of activated carbon???lignin composites prepared at different pH values was evaluated. As the pH increased, the compressive strength decreased owing to the reduced hydrophobic interactions between the activated carbon and lignin, consistent with the SFA results. These quantitative results regarding lignin interactions can advance the potential use of lignin as an eco-friendly biomaterial