Lignin Core Research Articles

Revealing the structural changes of lignin in Chinese quince (Chaenomeles sinensis) fruit as it matures

Chinese quince fruits (Chaenomeles sinensis) contain substantial amounts of lignin; however, the exact structure of lignin remains to be investigated. In this study, milled wood lignins (Milled wood lignin (MWL)-1, MWL-2, MWL-3, MWL-4, MWL-5, and MWL-6) were extracted from fruits harvested once a month from May to October 2019 to investigate their structural evolution during fruit growth. The samples were characterized via High-performance anion exchange chromatography (HPAEC), Fourier transform–infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), thermogravimetric (TGA), pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS) and NMR (2D-heteronuclear single quantum coherence (HSQC) and 31P). The MWL samples in all fruit growth stages were GS-type lignin and lignin core undergoing minimal alterations during fruit development. The predominant linkage in the lignin structure was β-O-4′, followed by β-β' and β-5′. Galactose and glucose were the main monosaccharides associated with MWL. In MWL-6, the lignin exhibited the highest homogeneity and thermal stability. As the fruit matured, a gradual increase in the β-O-4′ proportion and the ratio of S/G was observed. The results provide comprehensive characterization of the cell wall lignin of quince fruit as it matures. This study could inspire innovative applications of quince fruit lignin and provide the optimal harvest time for lignin utilization.

An amphiphilic flocculant with a lignin core for efficient separation of suspended solids

The synthesis and application of conventional polymeric flocculants suffer from low flocculation efficiency and toxic residues; therefore, there is an urgent need to develop green and efficient flocculants and corresponding technologies. An amphiphilic copolymer (NPL) was synthesized by a “grafting to” strategy, using acrylamide, 3-chloro-2-hydroxypropyltrimethylammonium chloride, and kraft lignin. NPL consists of a lignin core that is attached to a polyacrylamide branched chain and a cationic group, and has the properties of an amphoteric polyelectrolyte. This structure demonstrates superior flocculation performance on suspended solids. Two typical clay suspensions, kaolin and bentonite, were selected to evaluate the flocculation performance of NPL. The results showed that the turbidity of kaolin and bentonite could be reduced to 2.08 NTU and 0.31 NTU, respectively, by using NPL in combination with polymeric aluminum chloride. The synergistic effect of charge neutralization and bridging was confirmed as the main mechanism of flocculation on the two clay suspensions by a series of characterization techniques, such as zeta potential determination, particle size analysis, and focused beam reflectance measurement. The treatment of high-turbidity wastewater/feedwater with NPL was investigated, and was found to significantly improve the effluent quality. The use of NPL is efficient, environmentally friendly, and technically feasible, and shows excellent potential for the treatment of wastewater.

An Amphiphilic Flocculant with a Lignin Core for Efficient Separation of Suspended Solids

An Amphiphilic Flocculant with a Lignin Core for Efficient Separation of Suspended Solids

Lignin-based thermoresponsive macromolecules via vitamin-induced metal-free ATRP

An environmentally-friendly process for the modification of lignin with thermoresponsive polymers was employed, providing well-defined structures with narrow molecular weight distribution (Mw/Mn = 1.44). We report a biocompatible vitamin-inspired photoinitiation system composed of two components i.e. riboflavin (vitamin B2) as a photosensitizer and ascorbic acid (vitamin C) as a mild reducing agent. Under blue light LEDs irradiation at 460 nm (5.0 mW cm−2) the presented two-component photoinitiation setup enables grafting of poly(ethylene glycol) methyl ether methacrylate (OEGMA500) from brominated lignin via metal-free ATRP approach. A series of cyclic voltammetry (CV) measurements were conducted to electrochemically characterize ATRP initiators, both brominated lignin and lignin-based polymers, confirming preserved chain-end functionality of the prepared macromolecules. Received polymers with lignin core and POEGMA side chains exhibited thermoresponsive properties, which were investigated by determination of number average sizes of macromolecules by dynamic light scattering (DLS) and transmittance by ultraviolet/visible (UV-Vis) absorption spectroscopy of KL-g-(POEGMA-Br)10 aqueous solution. The in vitro curcumin release studies showed that the active substance is released from drug-loaded micelles in a thermo-sensitive manner. Prepared lignin-based macromolecules will show wide application as crucial components of thermoresponsive coatings, potentially creating bioactive surfaces characterized by antifouling properties, controlling cell adhesion or used as biosensors, due to PEG-containing side chains in branched polymers.

Scalable Formation of Concentrated Monodisperse Lignin Nanoparticles by Recirculation‐Enhanced Flash Nanoprecipitation

AbstractA highly controllable and scalable process for fabrication of large amounts of concentrated lignin nanoparticles (LNPs) is reported. These lignin core nanoparticles are formed through flash nanoprecipitation, however, scaling up of the fabrication process requires fundamental understanding of their operational formation mechanism and surface properties. It is shown how a semicontinuous synthesis system with a recirculation loop makes it possible to produce flash precipitated lignin nanoparticles in large amounts for practical applications. The roles of the process parameters, including flow rates and lignin concentration, are investigated and analyzed. The results indicate that the LNPs are formed by a process of continuous burst nucleation at the point of mixing without diffusive growth, which yields nanoparticles of highly uniform size following a modified LaMer nucleation and growth mechanism. This mechanism makes possible facile process control and scale‐up. Effective control of the resulting nanoparticle size is achieved through the initial concentration of lignin in the injected solution. The impressive capability to produce suspensions of any predesigned multimodal distribution is demonstrated. The resulting nanofabrication technique can produce large volumes of concentrated LNP suspensions of high stability and tightly controlled size distributions for biological or agricultural applications.

Lignin fractionation from waste wood using organosolv treatment combined with membrane filtration

The purpose of this study was to investigate the characteristics of lignin fractionated from waste wood (WW) using a two-step process of ethanol organosolv pretreatment followed by ultrafiltration with membranes of different molecular weight cut-offs (1, 5 and 20 kDa). The different permeates obtained were characterized by fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA) and gel permeation chromatography (GPC). The analysis by FT-IR and NMR of these lignins showed that the lignin core was successfully separated from WW. TGA curves confirmed that the thermal properties of lignin fractionated by ultrafiltration were almost identical to each other. The results from GPC confirmed that fractionating of lignin was achieved by ultrafiltration. For the membrane fractionation process, values of molecular weight decreased as the cut-offs used to obtain the fractions became smaller. As a result, fractionating lignin by a two-step process allowed separating different fractions of lignin of different molecular weights yielded high purity without interference from existing pollutants in WW. The two-step process offers the possibility of using fractionated WW as an untapped source of lignin.

Selective Primary Alcohol Oxidation of Lignin Streams from Butanol-Pretreated Agricultural Waste Biomass.

Chemically modified lignins are important for the generation of biomass-derived materials and as precursors to renewable aromatic monomers. A butanol-based organosolv pretreatment has been used to convert an abundant agricultural waste product, rice husks, into a cellulose pulp and three additional product streams. One of these streams, a butanol-modified lignin, was oxidized at the γ position to give a carboxylic acid functionalized material. Subsequent coupling of the acid with aniline aided lignin characterization and served as an example of the flexibility of this approach for grafting side chains onto a lignin core structure. The pretreatment was scaled up for use on a multi-kilogram scale, a development that enabled the isolation of an anomeric mixture of butoxylated xylose in high purity. The robust and scalable butanosolv pretreatment has been developed further and demonstrates considerable potential for the processing of rice husks.

Value-adding of organosolv lignin: Designing mechanically robust UV-resistant polymeric glass via ARGET ATRP

Most lignin-based materials reported so far exhibit poor mechanical properties which still differ from the requirements of commercialization. Here, organosolv lignin was selected as raw materials and a series of lignin-graft-poly(methyl methacrylate) (OL-g-PMMA) copolymers were prepared via activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP). FT-IR, 1H NMR, and SEC analyses confirmed that PMMA chains have been successfully grafted onto organosolv lignin. Thermal analysis indicated that the lignin core could help increase the glass transition temperatures as well as thermal stability of OL-g-PMMA copolymers. More importantly, the introduction of lignin not only improved the mechanical properties of PMMA, but also induced UV resistance properties. This novel approach can be generalized to design natural biomass based copolymers with desired mechanical properties.

New Dual Functional PHB-Grafted Lignin Copolymer: Synthesis, Mechanical Properties, and Biocompatibility Studies.

Poly(3-hydroxybutyrate) (PHB) is a sustainable and biodegradable biopolymer from bacteria, but its brittle nature greatly limits its applications. In this study, we developed a lignin-PHB copolymer to enhance the mechanical properties of PHB. β-Butyrolactone was grafted onto the lignin core by using solvent-free ring-opening polymerization (ROP). Then different amounts of lignin-PHB copolymers were blended into PHB and then engineered into nanofibers via electrospinning. The composite nanofibers with lignin-PHB copolymer exhibit much stronger mechanical properties than pure PHB fibers. Composite nanofibers with 2% lignin copolymer demonstrate the best mechanical performance with tensile strength increasing from 1.45 ± 0.36 MPa to 5.61 ± 0.63 MPa, Young's modulus increasing from 54.7 ± 1.2 MPa to 84.6 ± 10.0 MPa, and elongation increasing from 9.6 ± 2.2% to 93.5 ± 7.6%. Moreover, PHB/lignin nanofibers demonstrate tunable antioxidant activity, allowing the neutralization of excess free radicals in our body. Animal studies also demonstrate that the PHB/lignin nanofibers are nonirritating and biocompatible. Hence, these new PHB/lignin nanofibers hold great potential for biomedical applications.

Toxicological Assessment of a Lignin Core Nanoparticle Doped with Silver as an Alternative to Conventional Silver Core Nanoparticles.

Elevated levels of silver in the environment are anticipated with an increase in silver nanoparticle (AgNP) production and use in consumer products. To potentially reduce the burden of silver ion release from conventional solid core AgNPs, a lignin-core particle doped with silver ions and surface-stabilized with a polycationic electrolyte layer was engineered. Our objective was to determine whether any of the formulation components elicit toxicological responses using embryonic zebrafish. Ionic silver and free surface stabilizer were the most toxic constituents, although when associated separately or together with the lignin core particles, the toxicity of the formulations decreased significantly. The overall toxicity of lignin formulations containing silver was similar to other studies on a silver mass basis, and led to a significantly higher prevalence of uninflated swim bladder and yolk sac edema. Comparative analysis of dialyzed samples which had leached their loosely bound Ag+, showed a significant increase in mortality immediately after dialysis, in addition to eliciting significant increases in types of sublethal responses relative to the freshly prepared non-dialyzed samples. ICP-OES/MS analysis indicated that silver ion release from the particle into solution was continuous, and the rate of release differed when the surface stabilizer was not present. Overall, our study indicates that the lignin core is an effective alternative to conventional solid core AgNPs for potentially reducing the burden of silver released into the environment from a variety of consumer products.

Strong and biocompatible lignin /poly (3-hydroxybutyrate) composite nanofibers

Poly(3-hydroxybutyrate) (PHB) is an attractive biopolymer potential for various applications, but its brittle nature is a big handicap. In this study, we proposed lignin copolymers as mechanical reinforcement agents for PHB. A series of lignin copolymers (random and block) were synthesized via the solvent free ring-opening polymerization (ROP) of β-butyrolactone and/or ε-caprolactone onto lignin core. The lignin copolymers were characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). Next, these lignin copolymers were incorporated into PHB nanofibers as reinforcement fillers, in order to improve their mechanical properties. It is found that the lignin block copolymer with poly(ε-caprolactone) (PCL) segment followed by PHB segment (LPC + H) displayed the best mechanical improvement. Tensile strength of PHB nanofibers enhanced from 1.81 MPa to 3.13 MPa, and elongation at break increased from 15% of 55%. In the reinforced system, lignin plays as a rigid core, PCL acts a rubbery layer and PHB segment forms strong bonding with fiber matrix. Moreover, PHB/lignin nanofibers were demonstrated with superior biodegradability and biocompatibility, indicating that the new nanofibrous system holds great potential for biomedical applications.

Surfactant properties of PEGylated lignins: Anomalous interfacial activities at low grafting density

Lignin is a biopolymer in plant cell walls that has intrinsic interfacial functions and is produced in vast quantities but has found limited application as a surfactant. Here we demonstrate that low-density functionalization of anionic lignin derivatives with a corona of poly(ethylene glycol) (PEG) significantly augments their native interfacial activities, in contrast to previous studies of PEGylated lignins in which extensive functionalization was performed based on hydrophilic-lipophilic balance (HLB) predictions of solubility. Commercially available kraft lignin and lignosulfonate having high concentrations of carboxylate and sulfonate groups, respectively, were PEGylated with monoreactive grafts having molecular weight 750, 2000, and 5000g/mol at constant grafting density and PEG fractions as low as 20% for the 750g/mol species whereas previous studies focused on 50% PEGylation of greater. Both classes of PEGylated lignin demonstrated modest reductions in air-water surface tension, which decreased monotonically with PEGylated lignin concentration to values as low as 50dyn/cm but did not demonstrate a sharp critical micelle concentration (CMC). However, the air-water surface tension was found to be relatively insensitive to both the chemistry of the lignin core and the graft length. In contrast, the cyclohexane-water interfacial tension was strongly dependent on lignin core, graft length, and concentration, with PEGylated kraft lignin driving the interfacial tension value to 3dyn/cm at a concentration of 0.1mg/mL that corresponded with an apparent critical micelle concentration while the PEGylated lignosulfonates had a weaker effect, with uniformly higher values of interfacial tension measured and no CMC observed. Finally, cyclohexane-water emulsions were prepared, and the volume fraction of the emulsion phase was much greater for PEGylated kraft lignin than for PEGylated lignosulfonate, suggesting formulations based on kraft lignin are significantly more effective at stabilizing oil-water interfaces. This disparity suggests that specific interactions between the lignin core and the non-aqueous phase may augment interfacial activities.

Lignopolymer Superplasticizers for Low-CO2 Cements

Grafting hydrophilic polyacrylamide from a kraft lignin core results in a lignopolymer that effectively plasticizes portland cement paste. Here, the potential of this sustainably sourced lignopolymer is examined for improving the workability of portland cement blended with two natural, finely divided mineral materials (kaolin clay and clinoptilolite zeolite), which can be potentially used in combination with portland cement as a means to reduce the cement clinker content and the concomitant embodied energy and greenhouse gas emissions in concrete. Both mineral materials are known to affect cement hydration reactions but can significantly reduce workability when blended with portland cement, presenting a challenge for their practical large scale use.1,2 The plastic behavior of mineral-cement combinations dosed with polyacrylamide-grafted kraft lignin was compared to the behavior of those with a lignosulfonate developed for plasticizing portland cement and a commercial polycarboxylate ether (PCE). Compared ...

Tunable Pickering emulsions with polymer-grafted lignin nanoparticles (PGLNs)

Lignin is an abundant biopolymer that has native interfacial functions but aggregates strongly in aqueous media. Polyacrylamide was grafted onto kraft lignin nanoparticles using reversible addition–fragmentation chain transfer (RAFT) chemistry to form polymer-grafted lignin nanoparticles (PGLNs) that tune aggregation strength while retaining interfacial activities in forming Pickering emulsions. Polymer graft density on the particle surface, ionic strength, and initial water and cyclohexane volume fractions were varied and found to have profound effects on emulsion characteristics, including emulsion volume fraction, droplet size, and particle interfacial concentration that were attributed to changes in lignin aggregation and hydrophobic interactions. In particular, salt concentration was found to have a significant effect on aggregation, zeta potential, and interfacial tension, which was attributed to changes in solubility of both the kraft lignin and the polyacrylamide grafts. Dynamic light scattering, UV–vis spectroscopy, optical microscopy, and tensiometry were used to quantify emulsion properties and nanoparticle behavior. Under all conditions, the emulsions exhibited relatively fast creaming but were stable against coalescence and Ostwald ripening for a period of months. All emulsions were also oil-in-water (o/w) emulsions, as predicted by the Bancroft rule, and no catastrophic phase inversions were observed for any nanoparticle compositions. We conclude that lower grafting density of polyacrylamide on a lignin core resulted in high levels of interfacial activity, as characterized by higher concentration at the water–cyclohexane interface with a corresponding decrease in interfacial tension. These results indicate that the interfacial properties of polymer-grafted lignin nanoparticles are primarily due to the native hydrophobic interactions of the lignin core. These results suggest that the forces that drive aggregation are also correlated with interfacial activities, and polymer–nanoparticle interactions are critical for optimizing interfacial activities. Controlled radical polymerization is a powerful tool for polymer grafting that can leverage the intrinsic interfacial functions of lignin for the formation of Pickering emulsions.

An environmentally benign antimicrobial nanoparticle based on a silver-infused lignin core.

Silver nanoparticles have antibacterial properties, but their use has been a cause for concern because they persist in the environment. Here, we show that lignin nanoparticles infused with silver ions and coated with a cationic polyelectrolyte layer form a biodegradable and green alternative to silver nanoparticles. The polyelectrolyte layer promotes the adhesion of the particles to bacterial cell membranes and, together with silver ions, can kill a broad spectrum of bacteria, including Escherichia coli, Pseudomonas aeruginosa and quaternary-amine-resistant Ralstonia sp. Ion depletion studies have shown that the bioactivity of these nanoparticles is time-limited because of the desorption of silver ions. High-throughput bioactivity screening did not reveal increased toxicity of the particles when compared to an equivalent mass of metallic silver nanoparticles or silver nitrate solution. Our results demonstrate that the application of green chemistry principles may allow the synthesis of nanoparticles with biodegradable cores that have higher antimicrobial activity and smaller environmental impact than metallic silver nanoparticles.

Molecular architecture requirements for polymer-grafted lignin superplasticizers.

Superplasticizers are a class of anionic polymer dispersants used to inhibit aggregation in hydraulic cement, lowering the yield stress of cement pastes to improve workability and reduce water requirements. The plant-derived biopolymer lignin is commonly used as a low-cost/low-performance plasticizer, but attempts to improve its effects on cement rheology through copolymerization with synthetic monomers have not led to significant improvements. Here we demonstrate that kraft lignin can form the basis for high-performance superplasticizers in hydraulic cement, but the molecular architecture must be based on a lignin core with a synthetic-polymer corona that can be produced via controlled radical polymerization. Using slump tests of ordinary Portland cement pastes, we show that polyacrylamide-grafted lignin prepared via reversible addition-fragmentation chain transfer polymerization can reduce the yield stress of cement paste to similar levels as a leading commercial polycarboxylate ether superplasticizer at concentrations ten-fold lower, although the lignin material produced via controlled radical polymerization does not appear to reduce the dynamic viscosity of cement paste as effectively as the polycarboxylate superplasticizer, despite having a similar affinity for the individual mineral components of ordinary Portland cement. In contrast, polyacrylamide copolymerized with a methacrylated kraft lignin via conventional free radical polymerization having a similar overall composition did not reduce the yield stress or the viscosity of cement pastes. While further work is required to elucidate the mechanism of this effect, these results indicate that controlling the architecture of polymer-grafted lignin can significantly enhance its performance as a superplasticizer for cement.

Multi-arm carriers composed of an antioxidant lignin core and poly(glycidyl methacrylate-co-poly(ethylene glycol)methacrylate) derivative arms for highly efficient gene delivery.

A lignin-based copolymer with good biocompability was successfully prepared via atom transfer radical polymerization (ATRP) for efficient gene delivery. Kraft lignin was modified into lignin-based macroinitiators and then poly(glycidyl methacrylate)-co-poly(ethylene glycol)methacrylate (PGMA-PEGMA) side chains were prepared via ATRP grafting onto lignin. Ethanolamine was sequentially functionalized onto lignin-PGMA-PEGMA and a cationic lignin-PGEA-PEGMA copolymer consisting of a lignin core and different-length PGEA-PEGMA side chains was produced. Lignin-PGEA-PEGMA copolymers could efficiently compact pDNA into nanoparticles with sizes ranging from 150 to 250 nm at N/P ratios of 10 or higher. The gene transfection efficiency depends greatly on the mass percentage of PGEA units and the N/P ratio. The lignin-PGEA-PEGMA with 46.9% (mass%) of PGEA units (i.e. LG100) has highest transfection efficiency in comparison with the copolymers with a lower amount of PGEA units. In addition, LG100 has high transfection efficiency under serum conditions, which is comparable to or much higher than PEI control in HEK 293T and Hep G2 cell lines. More importantly, lignin-PGEA-PEGMA copolymers have excellent antioxidant activity. The novel cationic lignin-PGEA-PEGMA copolymers can be promising gene carriers for gene delivery.

Biomass-based thermogelling copolymers consisting of lignin and grafted poly(N-isopropylacrylamide), poly(ethylene glycol), and poly(propylene glycol)

This paper reports the synthesis and characterization of a series of biomass-based thermogelling graft copolymers using atom transfer radical polymerization (ATRP) technique, which are composed of a lignin core and multiple arms of graft polymer chains, where each graft consists of a block of poly(N-isopropylacrylamide) (PNIPAAm) and a block of brush-like random copolymer of poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG). A few control copolymers with different chain architectures and/or compositions were also synthesized for comparison purposes. It was found that the lignin-based PNIPAAm-block-PEG/PPG copolymers were thermo-responsive in aqueous medium. The aqueous solutions of the copolymers displayed thermogelling behaviors, turning from a sol at low temperatures to a hydrogel at temperatures around 32–34 °C, and further to a dehydrated gel at higher temperatures. The thermogelling copolymers had very low critical gelation concentrations ranging from 1.3 to 2.5 wt%. The thermo-responsive rheological properties were investigated. The elastic modulus G′ and viscous modulus G′′ of the copolymer solutions were very low at low temperatures, and increased at higher temperatures, and then crossed over at their gelation temperatures, with G′ dominating G′′ after the gel formation. The block architecture of the lignin-based PNIPAAm-block-PEG/PPG copolymers is key to their hydrogel formation, because the lignin-based PNIPAAm-random-PEG/PPG copolymer with the same monomer ratio, as a control polymer, could not form hydrogels at any temperature, whose solution only turned from transparent to turbid when the temperature was increased.

Polymer-grafted lignin surfactants prepared via reversible addition-fragmentation chain-transfer polymerization.

Kraft lignin grafted with hydrophilic polymers has been prepared using reversible addition-fragmentation chain-transfer (RAFT) polymerization and investigated for use as a surfactant. In this preliminary study, polyacrylamide and poly(acrylic acid) were grafted from a lignin RAFT macroinitiator at average initiator site densities estimated to be 2 per particle and 17 per particle. The target degrees of polymerization were 50 and 100, but analysis of cleaved polyacrylamide was consistent with a higher average molecular weight, suggesting not all sites were able to participate in the polymerization. All materials were readily soluble in water, and dynamic light scattering data indicate polymer-grafted lignin coexisted in isolated and aggregated forms in aqueous media. The characteristic size was 15-20 nm at low concentrations, and aggregation appeared to be a stronger function of degree of polymerization than graft density. These species were surface active, reducing the surface tension to as low as 60 dyn/cm at 1 mg/mL, and a greater decrease was observed than for polymer-grafted silica nanoparticles, suggesting that the lignin core was also surface active. While these lignin surfactants were soluble in water, they were not soluble in hexanes. Thus, it was unexpected that water-in-oil emulsions formed in all surfactant compositions and solvent ratios tested, with average droplet sizes of 10-20 μm. However, although polymer-grafted lignin has structural features similar to nanoparticles used in Pickering emulsions, its interfacial behavior was qualitatively different. While at air-water interfaces, the hydrophilic grafts promote effective reductions in surface tension, we hypothesize that the low grafting density in these lignin surfactants favors partitioning into the hexanes side of the oil-water interface because collapsed conformations of the polymer grafts improve interfacial coverage and reduce water-hexanes interactions. We propose that polymer-grafted lignin surfactants can be considered as random patchy nanoparticles with mixed hydrophilic and hydrophobic domains that result in unexpected interfacial behaviors. Further studies are necessary to clarify the molecular basis of these phenomena, but grafting of hydrophilic polymers from kraft lignin via radical polymerization could expand the use of this important biopolymer in a broad range of surfactant applications.

Synthesis, characterization, and photoresponsive studies on lignin modified with (E)‐4‐(naphthalene‐1‐yl diazenyl)benzoic acid

In the present work, chromophoric system (E)‐4‐(naphthalen‐1‐yl diazenyl)benzoic acid was synthesized and incorporated into lignin core. The end hydroxyl group of lignin was modified with the free carboxyl group of the chromophoric systems by dicyclohexylcarbodiimide coupling. The products were characterized by means of UV–visible, fluorescence, FT‐IR, and NMR spectroscopic methods and subjected to photoresponsive studies. The results show that modification enhances the light absorption and light fastening properties of the chromophoric system. The photoinduced trans–cis isomerization on the newly developed photosensitive biopolymeric system and the chromophoric system were investigated. Results also show that the trans–cis photoisomerization and the reverse cis–trans thermal conversions of the photoactive groups were also assisted by the incorporation onto biopolymeric core. Copyright © 2014 John Wiley & Sons, Ltd.