PhD Dissertation: MEHMET SİNAN TÜBCİL, POLYOXAZOLINE-BASED FUNCTIONAL MODIFICATION OF NONWOVEN DIAPER TOPSHEETS FOR THE PREVENTION OF IRRITANT DIAPER DERMATITIS IN INFANTS, Date & Time: June 15, 2026 – 9:00 AM, Place:FENS G029

POLYOXAZOLINE-BASED FUNCTIONAL MODIFICATION OF NONWOVEN DIAPER TOPSHEETS FOR THE PREVENTION OF IRRITANT DIAPER DERMATITIS IN INFANTS

MEHMET SİNAN TÜBCİL
Molecular Biology, Genetics and Bioengineering, PhD Dissertation, 2026

Thesis Jury

Asst. Prof. Bekir DIZMAN (Thesis Advisor)

Asst. Prof. Nur MUSTAFAOĞLU

Prof. Bahattin KOÇ

Prof. Gülnur ARABACI

Prof. Neslihan ŞAKİ

Date & Time: June 15th, 2026 – 9 AM

Place: FENS G029

Keywords: Irritant diaper dermatitis (IDD), diaper topsheet, nonwoven surface

modification, pH buffering, enzyme inhibition

Abstract

Irritant diaper dermatitis (IDD) is a frequently observed inflammatory skin disorder in infants, primarily linked to sustained contact with urine, feces, moisture, mechanical friction, elevated pH, and fecal enzymes. Since infant skin has an immature barrier structure and a less developed acid mantle, the diaper-skin interface represents a vulnerable microenvironment where biochemical and mechanical stressors may act together. Although modern disposable diapers have improved absorbency and dryness, functional topsheet modifications are still needed to reduce irritation-related biochemical triggers while maintaining skin compatibility.

This dissertation investigates structural and chemical modifications of the diaper topsheet layer to prevent dermal reactions in infants. Nonwoven surface treatments for disposable hygiene products were reviewed, and diapering practices in Turkey and worldwide were comparatively evaluated. Amphiphilic polyoxazoline-based copolymers with carboxylic acid functionality were synthesized through succinylation of poly(2-propyl-2-oxazoline-co-ethyleneimine). The resulting S-PPrOZ-PEI polymer was characterized by NMR, FTIR, SEC, DSC, TGA, buffering capacity, water uptake, dip-coating, and contact angle analyses.

The developed polymer exhibited properties suitable for diaper topsheet applications, including amphiphilic behavior, buffering capacity, moisture affinity, and applicability onto polypropylene nonwoven substrates. A fecal enzyme-inhibiting finishing formulation was then designed to modulate the diaper microenvironment through acidic buffering and ZnO incorporation. Acidic buffering reduced urease-associated ammonia formation by approximately 97% and lipase activity by approximately 82%. Dermatological tests showed no irritation or sensitization, while microbiological tests indicated only mild antimicrobial effects below biocidal thresholds. Overall, this thesis presents a skin-compatible, pH buffering topsheet formulation for reducing enzyme-driven irritation mechanisms in IDD.