Synthesis of pH- and Temperature-Responsive Hydrogels

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Questions and Answers

What initiator was used in the synthesis of chitosan-p(MAA-co-NIPAM) hydrogels?

Calcium chloride

Sodium bicarbonate

Ammonium persulfate (correct)

Potassium sulfate

Which peak corresponds to the PMAA in the FTIR analysis?

2930 cm−1

1155 cm−1

1648 cm−1

1716 cm−1 (correct)

What was the primary solvent used to dissolve chitosan in the preparation process?

Diethyl ether

Sodium hydroxide solution

Glacial acetic acid (correct)

Ethanol

What does the area between the baseline and the peak represent in FTIR results?

Peak area Signup and view all the answers

What is the purpose of the ratio of peak area values in the study?

To indicate relative changes in composition Signup and view all the answers

At what resonance frequency was the solid-state 13 C NMR measurement carried out?

100.62 MHz Signup and view all the answers

Which component is NOT mentioned as part of the hydrogel synthesis process?

Acrylic acid Signup and view all the answers

What aspect of the hydrogels was assessed by measuring their zeta stability?

Colloidal stability Signup and view all the answers

What reaction time resulted in high zeta potential values?

120 min Signup and view all the answers

What happens to the hydrodynamic diameter when the reaction time is extended from 120 min to 180 min?

It increases Signup and view all the answers

What effect does increasing temperature have on the zeta potential?

It slightly increases Signup and view all the answers

How does the PNIPAM content affect the zeta potential at extended reaction times?

It covers the outer surface, lowering zeta potential Signup and view all the answers

What was the extent of the shrinkage diameter compared to maximum swelling observed?

50 percent Signup and view all the answers

What was the effect of ionization of PMAA on the stability of the hydrogels?

It did not affect the stability at all Signup and view all the answers

What interaction was primarily broken due to increased temperature?

Hydrogen bonds Signup and view all the answers

At what reaction time is the hydrodynamic diameter smaller than that at the subsequent reaction time?

120 min Signup and view all the answers

What happens to the zeta potential as the pH increases above neutral levels?

It decreases due to cross-linking covering the surface. Signup and view all the answers

What role does SPAN 80 play in the formation of hydrogels?

It acts as a stabilizer by forming a monolayer film. Signup and view all the answers

How does reaction time affect the hydrogels synthesized for 30 minutes in terms of temperature stability?

They collapse at about 32 ◦ C. Signup and view all the answers

How does increasing temperature affect the stability of the hydrogels?

It improves the physical entanglement of the polymer chains. Signup and view all the answers

What effect does extending the reaction time to 120 minutes have on the hydrogel structure?

It produces high electrostatic repulsion impairing further shrinkage. Signup and view all the answers

What method was used to measure zeta potential in this study?

NANO ZS Zetasizer. Signup and view all the answers

Why does the zeta potential of hydrogels synthesized for 30 minutes appear high at low pH?

It indicates significant chitosan coverage on the surface. Signup and view all the answers

How does the reaction time impact the size of hydrogels at elevated temperatures?

Hydrodynamic size increases with longer reaction times at high temperature. Signup and view all the answers

What was the pH range examined for its effect on hydrogels?

1.68, 4.01, 7.4, 10.01. Signup and view all the answers

What is the main reason for the decrease in zeta potential over prolonged reaction times?

Increased cross-linking obstructing zeta potential effects. Signup and view all the answers

After how long did the polymer grow and reach a limitation?

60 minutes. Signup and view all the answers

What occurs when zeta potential is influenced by polymerization in various pH environments?

Zeta potential values fluctuate significantly. Signup and view all the answers

What was the effect of varying pH and temperature on hydrogels?

It affected the swelling behavior and particle size. Signup and view all the answers

What effect does the PMAA layer have on the structure of hydrogels at high pH?

It increases electrostatic repulsion within the structure. Signup and view all the answers

What kind of filter was used for the diluted hydrogels?

PTFE/L filter. Signup and view all the answers

What characteristic does the FTIR spectrum of chitosan display?

A broad peak at 3000–3600 cm−1. Signup and view all the answers

What type of hydrogels is characterized by swelling behavior that is sensitive to both salt and pH?

Partially hydrolyzed carrageenan hydrogel Signup and view all the answers

Which compound is primarily associated with enhanced antibacterial effects when delivered through graphene nanosheets?

Gentamicin sulfate Signup and view all the answers

What is an effect of comonomer hydrophilicity on the behavior of N-isopropylacrylamide copolymers?

Decreases lower critical solution temperature Signup and view all the answers

What characteristic of the superabsorbent hydrogel composite made of cellulose nanofibrils is highlighted?

Mechanical stability Signup and view all the answers

What is the main function of poly(N-isopropylacrylamide-co-methacrylic acid) hydrogels in drug delivery?

Pulsatile local delivery Signup and view all the answers

Which modification technique is used for carrageenan to achieve superabsorbent properties?

Grafting with polyacrylamide Signup and view all the answers

Which polymer is involved in the creation of temperature-sensitive interpenetrating networks?

Poly(N-isopropylacrylamide) Signup and view all the answers

What is the significance of the lower critical solution temperature in polymer applications?

Indicates the solubility of the polymer Signup and view all the answers

What peaks in the FTIR spectra indicate the presence of carbonyl groups in the chitosan-p(MAA-co-NIPAM) hydrogels?

1689 cm−1 Signup and view all the answers

What type of bond stretching is indicated by the peak associated with primary amines in the chitosan?

N–H stretching Signup and view all the answers

Which chemical groups show peaks in the region between 1700–1740 cm−1 in the FTIR spectra?

C=O of MAA Signup and view all the answers

At which peak do the C–H bending vibrations appear in the FTIR spectra of chitosan?

1421 cm−1 and 1384 cm−1 Signup and view all the answers

What is the significance of the peaks at 1638 and 1619 cm−1 in the FTIR analysis?

They represent C=C double bond formations in MAA and NIPAM. Signup and view all the answers

During the formation of the chitosan-p(MAA-co-NIPAM) hydrogels, how long did the reaction take before significant results were observable?

30 minutes Signup and view all the answers

Which of the following pairs of components are involved in the synthesis of chitosan-p(MAA-co-NIPAM) hydrogels?

Chitosan, MAA, and NIPAM Signup and view all the answers

Which of the following statements concerning the hydrogel structure post-reaction is correct?

Hydrogels exhibited significant inhomogeneity in shape. Signup and view all the answers

Study Notes

Synthesis and Evaluation of pH- and Temperature-Responsive Chitosan-p(MAA-co-NIPAM) Hydrogels

Chitosan-poly(methacrylic acid-co-N-isopropylacrylamide) [chitosan-p(MAA-co-NIPAM)] hydrogels were synthesized via emulsion polymerization.
The hydrogels are designed to be biocompatible, biodegradable, and multi-responsive, making them suitable for drug delivery systems.
Copolymerization of MAA and NIPAM with chitosan creates the chitosan-based hydrogel.
Fourier transform infra-red (FTIR) spectroscopy confirmed successful hydrogel production.
PNIPAM coating on the hydrogel influenced its stability during synthesis.
Chitosan and PMAA increased the hydrogel's zeta potential.
Chitosan controls hydrogel shrinkage above body temperature.
The hydrogels respond to both pH and temperature, enhancing their performance as drug carriers.

Introduction

Hydrogels are materials that absorb water in response to physical, chemical, or biochemical stimuli.
They are used as drug carriers due to their extended duration in the body without substantial health risks.
Chitosan, a natural polymer, is utilized for its biodegradability and biocompatibility.
Chitosan is modified by crosslinking to create pH and temperature sensitivity to enhance drug delivery performance.
Crosslinking chitosan with PNIPAM results in hydrogels with low toxicity, and tailored drug release profiles.
Chitosan crosslinked with PMAA hydrogels respond to ionic strength variations (osmotic pressure).

Experimental

Materials such as NIPAM, MBA, chitosan, Span 80, and acetic acid were used.
Chitosan-p(MAA-co-NIPAM) hydrogels were synthesized using emulsion polymerization with ammonium persulfate (APS) as an initiator.
The procedure involved controlled dissolution of chitosan, addition of MAA and NIPAM, and addition of crosslinker (MBA) and emulsifier (Span 80).
Various reaction times (RT30, RT60, RT120, RT180) were used to investigate the synthesis process.
Freeze-drying and dialysis purified the synthesized hydrogels.

Hydrogel Characterization

Field emission scanning electron microscopy (FESEM) examined the morphology.
Fourier transform infrared spectroscopy (FTIR) identified functional groups within the hydrogels.
Fourier transform infrared spectroscopy (FTIR) was used to investigate the interaction between different monomers such as PMAA, PNIPAM and chitosan throughout the reaction.
13C Nuclear Magnetic Resonance (13C NMR) analysis confirmed the incorporation of MAA, PNIPAM and chitosan.

Response to pH and Temperature

Zeta potential measurements evaluated the stability at various pH values (1.68, 4.01, 7.4, 10.01).
Zeta potential measurements also examined the effect of temperature variations from 25°C to 55°C.
Dynamic light scattering (DLS) measured the swelling/de-swelling behavior of hydrogels at different pH values.
Swelling/de-swelling behavior was studied at 37°C with dynamic light scattering (DLS).
Volume phase transition temperature (VPTT) was investigated to understand temperature-dependent properties.

Conclusions

Emulsion polymerization successfully synthesized chitosan-p(MAA-co-NIPAM) hydrogels.
Reaction time significantly affected the hydrogel structure and properties; suitable reaction times were identified.
Hydrogel structure was altered by extending the reaction time; controlled ratios of MAA, PNIPAM, and chitosan were established.
The hydrogels exhibited responsive behavior to pH and temperature changes.
The hydrogels have potential application as drug delivery carriers.

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Description

This quiz explores the synthesis and evaluation of chitosan-based hydrogels that respond to pH and temperature changes. Learn about the copolymerization processes, biocompatibility, and drug delivery applications of these innovative materials, including key characterization techniques like FTIR spectroscopy.